I've long held the theory that humans have differing degrees of rudeness because it breaks deadlocks like "after you", subdivide-or-finish the divisible food item, and who takes the last piece. (In places that were too polite, I have seen the last piece of a cake go stale uneaten.)
My friend and I used to have a serious case of "after you" deadlocks during our studies; we would get stuck in front of a door insisting the other goes through first. We eventually figured out a simple solution - if we found ourselves about to get stuck in another "after you" loop, we'd play rock-paper-scisors, and the loser had to go first. It quickly became almost a second nature for us, and it looked pretty confusing/hilarious to people stuck behind us in the queue.
I live by the rule that I never follow an "after you" with a "no, after you" without good reason. If they want demonstrate their politeness, why compete?
The obvious reason is because you get to play rock-paper-scissors.
The less obvious reason is that after a certain number of back-and-forths, you can interrupt the other person saying "aft-", cut them in line sideways so you both sort of swoop through the doorway, which then leads to a warp zone.
