Before AI a large pull request was enough effort to make that you could assume good faith work on the part of everyone. Likely even if it is bad for architectural reasons it is solving an itch other users have and it is reasonable for them to want an explanation why you refused someone who made this much effort. And since the effort required meant it didn't happen often it wasn't a big deal to provide that.

These days large PRs are easy to create and so humans need to shut them down.

Whether or not someone is entitled to something has very little bearing on whether someone believes they are entitled to something (and are willing to waste everyone's time to make a stink about it). Having clear rules to point to, even after the fact, is surprisingly effective in mitigating that.

Or, put more bluntly, your belief in what people ought to feel entitled to has no bearing on what they do believe, and policy needs to address the latter, not the former.