The dealerships are making their money with various add-on packages now, to try to bump up the sale price. It isn't even in your favour to offer cash in most cases.

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.

If you take the 0% financing, you miss out on the $4,500 "customer cash" discount. They're just moving numbers around.

Talk to the federal reserve.

Car manufactures favor margins over moving metal. They've learned that long loan terms don't reduce sales, as most people define affordable to be, they can afford the monthly payment.

And since manufactures own the lending arm, and the sales arm, they enjoy higher margins, plus more in interest payments. Not everyone is going to qualify for that 0% interest. Plus, it keeps dealers happy because they can squeeze in bullshit fees to pad the sale price.