I wouldn't say that wanting to contribute to a shared commons of cool stuff isn't a human motivation.

And I'm not deriding those that build open source to boost their own reputation. I'm just much less interested in their work than the work of folks that are motivated by improving the commons (even if they get no credit).

You are imagining people in your head. Most serious open source contributions are paid for. Per FSF survey overwhelmingly so.

Because, they are a lot of work. They are not hobbies or kitchen soup two hours a week effort. These require a lot of sustained effort and time, that would either takes time from your paid job, or would make you effectively work 60 hours a week which means you have no other life.

End result is that these are paid positions, so.