Why are some men boobmen and why are some buttmen? Do you think there is a reason?

This question is mostly to guys but lesbians or women are welcome to answer. I am a boobman but rarely I will find a butt attractive. I've got to say that staring at a butt is less dangerous then boobs. Sorry, I digress. Do you think there is a biological reason that some men prefer buts and some boobs? Freud would say that it has to do with if you were breastfed or not LOL but I don't put much stock into that. Anyway, boobmen, buttmen, do you have any idea why you are attracted? Just wondering if there is some rhyme or reason to it...