All of them, in a way. We don’t sign on to social rules we just kind of learn them, usually from our parents, then from other kids. Someone who’s never been in an elevator might face inwards. I’m from the North of England. The first time I took a ride on the London tube I was 30ish, and I was completely unaware of the incredibly complex and subtle social rules at play there. I made eye contact and even smiled. I tried to strike up a conversation. This was completely wrong to do, it turns out. I never agreed to be so unfriendly, specifically on the tube, but now, I am.

So anyway to answer your question, the weird requirement to sort of suppress your humanity on public transit in big cities is maybe necessary, definitely not hilarious, but very, very strange.