Yeah because we could not afford to keep up with the "hours" on our cars and most drivers would not pass the physical, let alone the book.
Edit- I will say this tho. I still toy with putting a Hobbs hours gauge in the Dart race car. Why dont more cars run hours gauges?
Race car engine wear aint measured in miles.
All the hot race boats run hours. Heck APUs, tractors everything besides cars run hours.
