As kids, we learn all the rules that get us a good mark in “Plays well with others”. One of them is how to form a queue or line and act like good little kids that do not frazzle our saintly elementary school teachers more than necessary.
This carries over into being a supposed adult. When I went to pick up my son at summer camp recently, they had an elaborate procedure in place to guarantee the kids’ safety. Everyone had to present a form of ID to pick up their child, and it was compared to a list of valid parents and caretakers. This operation took a lot of time, and so everyone automatically formed a line.