When I was a kid, we had this truck that my dad was working on. At one point he had to push it out of one bay of the garage and into the second bay... I think I was about 5 or 6 and wanted to help, so he had me push the truck from the bed.
I did figure out that it was a way to get me out from underfoot as the adults moved a heavy truck by hand. It was probably the safest place for a 5 year old to be.
I'd guess the same sort of thing is going on here, you put the useless dumb guy in a place where you know he can't fuck shit up or hurt himself.