I seem to remember taxi drivers who regularly don't wear seatbelts will leave their seats with the belts clipped in but sit on top of the belt... presumably this is to get around the warning beep that most modern cars have?
that can't be comfortable. if they can get used to that discomfort, they might as well wear the thing properly!
I think they might put the bead seat cover over the top of it. I've noticed lots of taxi drivers seem to do it, something about they don't need to legally wear the belt in case they get jacked, he/she can get out quicker... or so I heard...