You busted me. Big time.
Yeah, I have to confess, I love legs. I'm a little bit more of a legman in general. And unless I'm into amputees, that logic makes no sense for a legman. Though I suppose one difference is that what makes men's legs look good is different somewhat from what makes a woman's legs look good. (Hair being just one such factor.) And unlike, ass, legs never get appreciated unless they're fully exposed. Which isn't like checking out junk in the trunk.
I can get the biological rationale behind, say, men finding women's hips (or more particular, their bust-waist-hip ratios) or cleavage attractive. Less of a chance that you're about to hump a dude in a dark cave and all. But ass? What makes a man's ass look good to women is often very similar to what makes a woman's ass look good to men. Though the attraction to the female butt explosion thing, a la Kim Kardashian, seems to have no evolutionary preference connection I can come up with.