I have had the (not so novel, I admit) realisation that most intelligent people I know have had zero children, whilst most dumb people I know have had (at least) one. This was funny when it was the plot of a movie, now it's starting to worry me.
Did you consider your sampling bias?
The longer I live, the more I recognize that everybody has a role despite any apparent flaws. Take gays-- in a hunter-gatherer society, a clique not burdened by children to protect are free to become scouts or trailblazers; they have mobility. This childless-by-choice stuff is a modern invention and not an option for sexually-active adults otherwise.
We don't all have the same purpose. We're more like ants than we want to admit.
Natural selection optimizes for the human species over tens/hundreds of thousands of years. You won’t see a benefit in your lifetime.
Not having kids, well, you see the result in your lifetime (tends to be a slightly positive result).