We are all obsessed with sex. At the deepest, most primitive level, the earliest-developed parts of our brain dictate that we're obsessed with:
1. Not being eaten.
2. Eating
3. Sex
In that order. Basically, if we are to encounter another biological entity, the first thing that happens in our brains, at a barely higher level than the brain stem, is that the follwing questions are asked in rapid succession: "Will it eat me"? "If not, can i eat it?" "If not, can I shag it."
Obviously, we've engineered (1.) out of the equation to a significant degree, so much of our lives now revolve around (2.) and (3.).