Because every merge request and every merge comes with cost and (potential) more cost in the future.

Linux lately received a lot of fixes for drivers nobody has cared about for ages. They decided to remove them. Maybe they should have done this earlier, I don't know, but that happened because every code change comes with cost down the line. For real contributers, this cost is much more limited and they have a higher probability of burden the cost down the line.

Pure AI MRs are just rude, because it's just "here take this, don't really care what this is, but AI said it being good, I won't be around, so you will have to deal with this code after the merge and you better don't overlook anything, because I personally don't really know what I am doing, I only know how to have AI making something that looks convincing. Good luck fixing the bugs this change introduces".