And that's assuming there's only one chivalrous knight on the elevator. If two people have the same idea, they could end up in a brief "after you" standoff after everyone's exited.
Or sometimes you're about to turn onto a busy street (or cross one as a pedestrian), and you're just waiting for a gap in the cars when some nice driver slows down and waves you in. In many cases this is a nice thing, but in some situations it just makes everything worse. For example, if there's more than one lane going the same direction, and one guy in one lane tries to wave you in, while the drivers in the other lane don't give a shit and keep going. You can't turn until both lanes are stopped, so this nice driver is just holding up his entire lane and accomplishing nothing, and everyone behind him is now mad at him and you.
"Nobody else wants to stop!" you mouth at him silently, and he just keeps smiling and waving you in, like he doesn't see what the problem is. Man -- just go, dude. There will be a gap eventually, or maybe not, now that all the cars backed up behind you will be catching up where that gap was going to be.
Or how about stop signs, where some people disregard the fact there are clear rules about who goes first and consider it a chaotic Lord of the Flies situation where somebody has to take charge and they're willing to step up and start waving people through like they are the Stop Sign Lord. Confused drivers assume he will go first because he stopped first, but no, in his magnanimity he waves some random person through instead. This is not a complex situation that requires a level-headed leader to save the other drivers from chaos. You stop first, you go first. This is not hard to grasp. Oh, and blinking red traffic lights? Those are stop signs. Same rules. You're welcome.