Really the best question is:
Why the fuck are girls who have everything to lose and nothing to gain by being cunts the cuntiest cunts of them all? The sister in the Sopranos is a good example.... I can't count how many bovine shrews I've known like that.
Really though, I think on a graph with niceness on the y axis and prettiness/thinness on the x axis, it is a pretty sharp bell-curve. The kindest women I know are average-looking.
I have absolutely no sexual or other problem with average-looking women. I find probably over a good half of women in my age range to be completely fuckable.
My girlfriend, for instance, won't ever be a supermodel, she is slightly under the average weight for her height, has a cute face (most women do) and everything that makes a man tick.
Now, I have had opportunities with very exceptionally physically attractive women. Know what? I looked at the situation honestly and concluded that, since I don't do one-night-stands, it was completely out of the question because a serious relationship with any of these rude bimbos probably would end with her in a woodchipper.