I am a programmer, and I contribute plenty of FOSS code. Very often, I find a solution with some issues and submit PRs. I'm not arrogant enough to do a couple hours of work and charge $20 per download for it, and I'm not a useful enough idiot to work for free for Apple, so I guess that bars me from doing the same on MacOS (even though I have to work with it for work). I guess if some of my code is general enough, some well-meaning Apple FOSS users can port it over.
It's interesting to me how much comradery and work for the general community is done in the open for and among Linux and BSD users with only the expectation that others will do the same for them, but many Apple users I've run into are like you, treating the simple desire to make things better for people with absolute derision and disgust. I guess if you aren't maximizing profit, why do anything at all, right?