I think it's there not because people are generally expected to behave this way, but to have a framework of rules for when someone occasionally does, so that you can say that moderation decisions aren't completely arbitrary when you kick them out, or so you can say that someone that was arbitrarily kicked out was kicked out for the wrong reasons.

It seems like it could be useful for large and socially important projects with many contributors IMO but I'm not sure why <10 contributor projects pick up on the habit.