I used to ask guys out.  I had sympathy for how hard it must be for them to
have that burden.  (Man, are we ever well-trained in this society, if women
can be tricked into feeling sorry for men’s burden and accepting how
unsympathetic most men are about ours.)  The men I asked out were the
shy guys, the ones who clearly had interest and expressed that to mutual
friends even, but who were still too awkward and insecure to make moves
of their own.  
It’s not as if I was outright rejected.  They were all thrilled…at first.  But an
insecure man has the attitude of Groucho Marx–he won’t belong to any
club that would have him as a member.  One day he is fantasizing over
you and staring with desire from across the room; the next day you go over
and do what you believe will be seen as a good thing by taking the
pressure off of him and removing rejection from the picture; before long,
he’s strutting around like a peacock, looking at other women, ignoring or
disdaining his former crush, because deep down, he knows how it’s
supposed to work: women don’t ask men out, because they don’t have to.  
If a woman asks a man out, she must not be getting asked out.  Since the
insecure guy thought so little of himself in the first place, he considers that
this girl must have been especially goddamn desperate or insecure herself
to ask him out.  Having been asked out though, his self-image is
bolstered, and so now, he’s beginning to think he could do better.  

And then there's the simpler explanation:

I think we can probably all agree at this point that we do not live in a world
of good guys who wear white hats and bad guys with pencil-thin
moustaches.  It’s hard to tell definitively who is safe and who is a threat
until you’ve already let them get so close that if you are in danger, it’s too
late.  We can’t tell for sure whether a guy is truly good just on the basis
that he seems nice.  You all may wish that we had more compassion and
would take chances.  But here’s a fact: if you don’t tend to date much or at
all, if you don’t hang out with people regularly, if you are just that big a
loner or that socially inept or that painfully shy, hey, my heart goes out to
you!  Really it does!  But you have to acknowledge what that says to the
average observer.  We wonder what’s wrong with you.  We worry that you
might be one of those “quiet types” who turns out to be a psycho-killer with
heads in the freezer.  We simply just don’t know, and this world is too
filled with perils for us to be generous of spirit and take that leap to find
out.  
It’s unfair to the shy guys that the not-so-shy guys ask women out so
freely.  It’s unfair to the good guys that the bad guys have made women so
guarded and suspicious.  But you know what?  It’s a hell of a lot more
unfair that these factors have led to our feeling threatened and jumpy and
distrustful every moment of the damned day and twice as much at night.  
And the fact is that since we know that a shy guy is as likely to turn out to
be a sicko as a confident one, we might as well spare ourselves the
trouble of asking guys out.  
You want to talk about the inequity and burden of it all?  Try complaining to
the guys you see hitting on women all the time!  Say, “Hey, man, why don’t
you all starve the women for attention and see what happens?”  It’s a
slapstick comedy in the tradition of Aristophanes at the very least.  But as
long as we get asked out by the great majority of men, we’re not going to
be too motivated to take the active role in courting.  In the standards of this
society, it is normal for men to be at least willing to approach women, if not
particularly at ease doing so.  If you can’t do it at all, accept the fact that
we will wonder what is wrong with you or at best simply assume that you
are not interested.  

And then there is the cruelest answer, the Reality Check.  I know this flies
in the face of all the pornography-inspired expectations of life you may
have developed, after years of watching utter schmo’s banging much
more attractive young women with little or no situational persuasion.  The
simple fact of life you need to get over is that there really are Leagues.  If
you have had a crush on this girl for ages and you have watched her go
out with all these really good-looking jerks, and you have hinted repeatedly
to her that you would treat her really well, and you have grown to resent
her for not being interested in you, then you need to look around at the
women you have known who acted that way toward you but to whom you
were not attracted.  It’s like the food chain; we’ve all got people higher and
lower than ourselves, and we need to accept the fact of our position on it.  
If I told you that fear of being eaten by a shark was “all in your head” and
you “need to rise above it,” that going up to the shark and presenting
yourself in a confident and honest way would be a reasonable beginning to
a meaningful interaction with it, would you jump into shark-infested waters
with a smile?
So why is it that a man has no apparent awareness of when he is aiming
outside of his league?  A month or so ago, I was in a cab with a very
obnoxious driver who lectured me for nearly the entire trip about proper
cab etiquette, despite the fact that I had in no way violated that protocol. At
some point in the diatribe he asked me what I did for a living, and I said, “I’
m a model.”  He also mentioned repeatedly along the way how attractive
he found me and how well I dressed, etc.  Then he asked me out, and he
was damn pushy about it.  And I found myself kind of awed at the concept
of it: a man at least twice my age, not remotely the sort of attractive or
charming he’d have to be to overcome that instant barrier, hitting on me
and then giving me his number in case I change my mind.  
If the women you like are in all honesty far more attractive than you, then
you need to be able to make up for that with some other quality that will
make you stand out.  You’re arguing with me right now, aren’t you, saying
that you see pretty women with less-pretty men all the time?  Yes, and I
guarantee you they didn’t have the immense luck you’re wishing for, that
the pretty women saw them sitting quietly and approached them.  Some of
them are smart, or artistic, or funny, etc.  Others may have money (I’m
ashamed to acknowledge there are still some women out there for whom
that’s a motivating factor).  Most of these guys, though, are simply
outgoing.  That is often sufficient when it comes to dating.  Women like
guys who aren’t completely petrified of them.
The league thing works both ways; don’t think I’m saying it’s only men
who have to learn to live with reality.  There are all kinds of men I think I
wouldn’t have a chance in hell with, and I’m fine with that.  My boyfriend
knows I like a kind of fucked up nose on a man, like maybe he’s broken it
in the past or something.  It’s no big deal, just a physical attribute I have
always responded to.  Apparently, his best friend’s wife shares my
particular esthetic leaning, and he reported to me that he and his friend
had agreed that if we ever met Luke and Owen Wilson, they’d never see
us again.
Of course, I merely said, “Oh please,” and blew it off.  Because the real
answer would only lead into a much longer discussion than the idea merits
and end up insulting everyone involved (except, perhaps, the Wilson
brothers).
The real answer goes like this: A. We would never be in a situation for
Luke and Owen Wilson to get a glimpse of us; and B. they wouldn’t give a
shit even if they did see us.  
That is the reality of the scenario as presented.  However, it implies that A.
we would leave you for a couple of movie stars if we had the chance, and
B. we are settling for you, so you must be losers.
That is not at all the truth, so I didn’t go there.  But take my boyfriend out of
the equation and put me in a position to be spotted by Luke Wilson, and I
still have no delusion about his being transfixed with desire for me.  
Please.  That is the reality of the situation.  
If you are going after a job, and you know that your resume doesn’t look
impressive, do you belligerently say Screw ’em if they can’t see through
that to know how great I am anyway!  Or do you write a great cover letter,
dress well for the interview, and do your best to sell yourself to the
employer?
So why when dealing with women, would you choose to defiantly avoid
giving them any reason to develop an interest in you?  You can sit around
and believe that you’re a nice guy, and they should be able to see that, but
give me a break!  Every serial killer who was ever described as a
seemingly nice, normal guy has kind of blown that one for you.  If we are
just as likely to be raped and murdered by the seemingly nice guy who
asks us out as the seemingly nice guy who never asks us out, what the hell
is our incentive to go out of our way and approach you?
There is a brilliant film by Todd Solondz, called Happiness.  My favorite of
the many plots involves Philip Seymour Hoffman, Lara Flynn Boyle, and
Camrynn Manheim as neighbors on the same floor of their apartment
building.  Hoffman is obsessed with Boyle, who has never given him a
second glance except maybe to make sure he wasn’t standing too close to
her in the elevator.  Manheim is infatuated with Hoffman and all but does
the Dance of Seven Veils trying to get his attention, but he is rude and
dismissive toward her.  When Hoffman manages to get invited in by Boyle
based on her impressions of him only over the phone, she sits in awkward
silence for a minute before saying flatly, “This isn’t going to work.  I’m not
attracted to you.”