I have bought two used carts, both from the same golf course. When I bought them, all I was given was a bill of sale that gave a description of the carts, as well as their serial numbers. The purchases were made in California, and therefore no attempt was made to license them. They were neighborhood cruisers only, and no, I didn't insure them.
I would have thought that if they were stolen, the bill of sale would suffice in proving ownership, much the same as a bicycle or other item that bears a serial number.