Why do most rock songs talk about love and most rap songs talk about sex?

I have heard a lot of rock and hip hop music and I have noticed that
when artists are talking about women, the rock songs usually talk
about love and breaking up and stuff like that and hip hop songs are
usually about wanting to bang chicks with big butts, and there's no
subtlety when they talk about it either. Even most r  b music is
about meeting girls at clubs and wanting to bang them.

Why is this?