Yeah but you don't contribute tens of thousands every year so if you're one of 3 contributors on a project so big it takes 100 hours of work a week to develop and maintain, that's not enough. The sad part is nearly nobody donates. And those who do, often do it one-off, not monthly. I'm guilty too. Most 100% unmonetized FOSS projects just don't have a stable revenue stream and to make it worse, the users can be real assholes, hounding the devs to work more or put someone else in charge to accept PRs quicker, etc.