If someone is disposing of a perfectly good used car to buy a new car, then someone else is going to buy their used car. And if they sell their old car and it's still decent, someone will buy that too. On down the line until you get to a car that isn't worth owning. And then that car is largely recycled, which is a better use for it than staying on the street polluting. No one is throwing out working electric cars, or gas cars that get good mileage and are in good operating condition.