I've never had an auto loan, is there a reason they couldn't just take the financing to get the incentives and then just pay it in full the next month?
They can come with early payoff penalties. It seems weird, but a loan is a thing that can be and often is packaged up and sold. If you pay it off, they have nothing to sell. Resale value of your loan is a factor in how much it costs.
Asset-backed securities are a strange world of value based on value that can either lead to market collapse (because someone misvalued them, see 2007-2008) or market efficiency (because more people can afford debt for stuff).
