Why do humans enjoy sex? Because prior to birth control having sex meant having kids, so people who had more sex had more kids and were more evolutionarily fit.

The recent invention of birth control broke this connection. Now someone can have tons of sex, but no kids, which means their evolutionary fitness is 0.

My guess is in the future, instead of just wanting sex, humans will evolve a desire to actually have kids.

The process is already happening now. People who actually want kids are creating the future generations, while people who only want sex are going childfree and evaporating out of the gene pool.