Well if you like the car, maybe he felt bad about the registration snafu, so maybe he was trying to get himself invited to a home cooked meal, his being divorced now. In exchange for waxing the car. His social life might be less than it was before the divorce and he thought you guys were nice? I could see where other people would really have been ticked off about the registrations, but you were pretty cool about it. Maybe he messes up little things like that a lot.