Also, all their childhood, sex was seen as this scary taboo thing their parents had to shelter them from learning about. So of course they're not going to immediately see sex in an any less taboo light the moment they start experiencing sexual attraction, that takes time.

When you're that young, you probably see sex as nothing but animalistic or lustful. You most likely want to do it at some point, but you can't really understand any beauty in it that's worthy of art.