Well to be honest, I don't understand why I find boobs attractive either. It is so hard to describe what is a nice pair of boobs, and what isn't. A lot of the time, one tiny thing can make the difference between a pair of nice boobs and a pair of gross boobs.
But I won't talk entirely about boobs.
I find women attractive because I do. Thats it really. Just like I don't find men attractive, am terribly afraid of heights, and love metal. I've tried to come up with whys and explanations, but they always fall short. Or when I think I have it, I remember a small detail, and my answer shatters.
I could get into the traits I find attractive in a woman, but when those same traits are put into a male body, it is not the same.
Was I raised to find women attractive and men not? Probably. I wasn't self-aware of that stuff until I was 12ish, so I can't honestly say. I won't get into what other people are raised to think about sexuality because that is really off topic and will start a flame war.
I'm sorry if that doesn't answer your question, but it really is the best I've got. Everything else I've tried makes less sense, or just sounds stupid, lol