For how long before those old vehicles are not practical? You will end up spending more in $$$ (or time) in the bodyshop than the car is worth. You will be rebuilding engines and transmissions. Sure it is possible to keep old cars working as daily drivers, but it is more cost effective to replace them after a while with something newer - modern assembly lines are very cheap ways to build something. (or course a car only a few years old is cheaper year)