Deplaning is another matter, of course, and generally I think that is actually quite efficient. People who hold up the lines are usually embarrassed and therefore police themselves. Every once in a while a fool holds up the line, but mostly each person adds no more time than the space ahead of them can allow.

Proof? Ok, how often do you find yourself in a secondary lineup, bag in hand, near the door of the aircraft? Nobody in your way now but the lineup ahead to get out of the corridor.