The paperwork may be simpler, but that does not earn them
anything.
Bank loans approved for your purchased vehicles brings them
commission.
If you are really prepared to buy the car full cash, you best
also let them salesperson knows that you are providing about
10%-20% of the car's worth as commission to them in cash.
If i am not wrong, they get about 5% commission for the sale of
car, so the remaining is from bank loan?