If you financed a car, that means the lender owns it until you pay it off. You agree in the loan contract that they'll take it back if you stop paying for it.
Plus, it's not like they repo it the day after a missed payment.
Most car loans are upside-down the second you drive it off the lot. It takes a long time to get out of negative equity, so the vast majority of people who have their cars repossessed don't have any equity built up.