You pose an interesting question. I think teenage boys are way more "obsessed" with genitalia and what it can do than girls. I'm sure there must be several reasons for this including the fact that anatomically, it's pretty much hanging out there all the time. Several of my nephews were obsessed with their junk as soon as they could figure out how to reach it.
Girls on the other hand have a lot more at stake, and at risk when it comes to sexual awakening. After all, they're the ones who can get pregnant. Also in most societies if a girl is sexually active at a young age she's a slut. Boys in the same situation tend to be admired.
I think it boils down to differences in how male and female brains are hardwired. Whatever the case, humans in general are constantly in search of satisfaction. Doesn't matter if it's sex, food, or an accomplishment. We want to feel good. The reason could be almost anything.