Suppose you sell a car in a private sale. Suppose further that the buyer didn't want to register the car right away. Suppose he asked you if you would leave the license plates on it for awhile. You just want the cash for the car. What do you care? What could possibly go wrong?
Well, the buyer could drive the car into a tree and seriously injure the young lady occupying the passenger seat. And, if that happens, in the eyes of the court, you still own the car.