Right, the hardness of the money is the check on credit expansion. Defaults are good, in the sense that they keep the system healthy. That interest payment could also be from a secondary market, where your stake in the car is bought by someone who believes the asset will appreciate, or if the original borrower makes enough money from its use to buy out the shareholder. It could get creative - the only point where I'd say it definitely raises ethical concerns is if the asset owner turns it into a coupon with payments. And that'll totally happen, so we should game it all out before trying to change the system.

I think you are missing the part where a certain segment of the population likes making sure they are completely insulated from the risk of managing your money for you while simultaneously ensuring that you are required to let them manage your money for you.