There is no one perfect girl that has all the qualities I want. Instead there are many girls who can please me in a lot different ways. This girl pleases me physically while this other girl has an exotic vibe that I like while this other girl is funny and that girl over there is sharp and witty. I like them all. And because I don’t currently want children, why pick one?
Regular sex, you’re thinking. Well if you can only get regular sex by committing to one other person, then maybe monogamy is best for you.