Honestly, I sometimes do. I contribute to free software, file bugreports and most of the time have a look at the code to see if I can fix it myself and hand in a patch. I tinker around with brand-new niche ideas. More often than not my (larger) contributions are to small projects and not the large ones. It’s not my hobby to fix Firefox. I think there are a lot of people like me.

And for Linux distributions and something like the F-Droid you have some maintainers on top, who often review every patch and new version.