I love sitting down an reading math books. Problem is, it's hard to do after a long day's work where I've been exercising my brain a lot. Especially when I have far more important and time sensitive things to do like cooking, eating, and cleaning up the messes I've made in the day. Sure, that doesn't take all the time, but between that and some time to be human, there's often not enough time + energy left. I think it is clear why so many people get so much knowledge when they're in school. Because your job is to learn. Why you can do so much in a PhD (sometimes, maybe not the best example) because you spend all day doing this. Now just imagine what OSS projects would be if people were doing it full time and not in addition to their jobs? Would the xz incident have happened? Would xz only have "two" maintainers?