Haven't they just turned it into a used car?
Yes, that's exactly what they are doing. But, dealers have a target.
I was working at GM Finance last year and their staff all get new Vauxhalls and Saabs every 6 months for virtually nothing. When they pick up their new car, they sign the order for the next one at the same time. The cars then go to the dealers to be sold as used. These semi-fake new sales are added to the overall total and allow GM to claim bigger sales and hence more popularity than they could otherwise.
I imagine December's a bad month for car dealers anyway, what with the closed days and people spending their money on presents and overeating.