Fat dudes vs. Fat chicks

Last night, we watched Balls of Fury. (Next week's post: Why one should never let one's stepsons select the movie for family night.) That film's one redeeming value was making other movies look good. ie. Star Wars Ep II suddenly seems to have brilliant dialogue! D-War has edge-of-your seat adventure! Will Ferrell is funny!

It also had THAT THING, you know, when the ugly/fat/nerdy guy ends up with the totally hot chick who is able to see his value and fall head over heels in love with him?  Yeah, THAT THING.

So, my question is, why does it never happen the other way around? Why doesn't an ugly/fat/nerdy chick end up with a totally hot guy who sees her true value and falls head over heels in love with her? And I don't mean movies like Never Been Kissed or She's All That or anything with Molly Ringwald in it because we all know that those chicks are seekritly HAWT, and the whole point of the movie is having the dreamy guy realize how sadly overlooked said HAWT chick's hawtness really is. No, I mean, why aren't there movies that have GROSS girls getting the guys? And specifically, I mean a Will Ferrell/Seth Rogan/David Spade/Dan Fogler level of grossness.

Is it because deep down inside, we believe that fat/ugly/nerdy chicks don't deserve to find love?