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.