I think people do that because they are closely involved with the code/plumbing. If they spend a week fixing a bug, they feel the weight of the changes that they made with every line that they wrote. If they just fixed the issue in passing and moved on to the next thing, I don't know if they would feel the same weight to contribute back.

More often than not, LLMs fixes an issue as a downstream user. So there's even less pressure to fix the issue. Because if library A does not work on Windows, it would just use mash together library B and C and something from itself to fix the work around it.