You're not giving them free money, you're getting them to pay you a lot more in total over many years by selling them a much more expensive vehicle up front. Instead of, say, $20k over 3 years, they can get $40k+ over 7 years for selling a product that doesn't remotely cost them twice as much to build. It's more profit for them.

These 0% 7 year loans are not coming from banks. They're coming from the car companies. They're a sales tool.