A driver does a better job of driving, more precise and more in control when they are fit. A tired driver gets sloppy and makes mistakes even just small ones. Even a crew chief or tuner makes better, clearer decisions when he is physically fit. Just imagine two weeks of long hard work days of 12-15 hours or more each day to get a car ready to race the long trip to the race track in another state. A person who is fit performs better under stress.
Champions win races, winning makes money, money pays the bills.
Keep fit and show me the money. Pick a professional class to aspire to, your selections in Australia are Top Fuel, Top Alcohol, Pro Stock. A good crew chief or car owner wants a known combonation in the engine and in the driver's seat. He can tinker with the engine combonation and if he goes astray he can go back to his standard tune up. He must have a driver who can perform everytime.