Why do guys look at girls butts?

Alright. Here goes, the true reason why guys look at girls butts is because, we all know, they are guys, and they have sick minds like that. But, if you have also ever looked at a guy, its not like he has boobs and a butt to look at, so we can't look at it. That's certainly another reason why they look at it, because we know that we can't look back.. But don't stress about them looking, its just looking, when they begin touching...well good luck! and also because they are curious about the texture of the butt and stuff like that.