I've heard stories of tire shops requesting the owner sit in the drivers seat while doing an alignment. There is no other safe way for the mechanics to simulate a 400lbs+ person in the drivers seat. This usually happens after the owner has tried to claim the tire warranty after wearing out the tires in a few thousand miles due to the the caster/camber angle to be way out of spec while they're inside. I'm also told that this is more prevalent with certain cars like the Volkswagen beetle which along with a few other cars have much more fat friendly doors, seats, and steering wheel position.