This happened while I waited in line at Subway about a month ago:
A customer who had been sitting at a table got up and walked in front of me. By way of explanation, she said, "Hi. I was sitting down." It wasn't worth arguing over, so I just said, "I see." The response I thought while saying this, however, was, "And I've been standing here. That's how waiting in line works."
Perhaps being isolated from people for so long during this pandemic has caused some of us to forget how to act.