Why do AI users complain about subs banning AI images?
Regardless of what actual reason they give, it's obvious they can't allow it. Because of the speed at which AI images can flood any sub. Even if you fancy yourself an "Ai artist" who wouldn't just prompt and post, there are many who will. They don't want to allow it then see AI image afer Ai image after AI image, then have to go through all that, some of who won't even declare that they're using AI, just to eventually find Ai free artwork.
That would render those subs unusable. If Reddit had an AI filter, and one that was actually reliable then that might lead to a different story, but as it stands, disallowing AI images is the forced move. There isn't anything to think about for the mods of these subs.
If you want to complain to anyone, complain to reddit for an AI filter.