I am surprised no-one this far has mentioned the (irrational) impulse of aisle seat passengers to make room for middle and window seat passengers to get out. Whenever I get the aisle seat, I have to fight the primate part of my brain that tells me that the passengers behind me in line want to move on, that I am keeping them from moving on, and that they are annoyed by my behaviour.

I know intellectually that deplaning won't happen any faster if I get up early, but if I do, the blame for the slowness then appears to lie with whoever is blocking the aisle between me and the exit, and not with myself.

This kind of social pressure may to a great extent explain why deplaning behaviour is the way it is.