science

It's literally the most natural thing in the world to equate reproductive effectiveness to worth. All life is "worth" their reproductive effectiveness. So not having sex is very relevant to our entire existence as a species.

As such, our mental faculties put a heavy punishment in the form of mental pain, i.e. "self-worth attached to getting laid", on this whole thing.

This has very little to do with societal expectations. It's simple biology. Not getting laid is supposed to be one of the worst things for an organism.

You're rationally right with what you say, but it's simply not very relevant. Rationality does not help with our most deeply rooted biological desires. The only thing that helps is getting them fulfilled, i.e. having sex.