The purpose of a racing sim is to get away from all the dreary practical aspects of being an automotive freak. You want it to simulate the looks, sound and physics of a car because you want to feel the thrills of owning a your dreamed car and rack as many miles as you wish with it. Would you be happy if racing games simulated the wheels of your car getting stolen? Or simulate how people scratch your car out of sheer envy? Or if it simulated that feeling of "I'd take my car out today but I don't have enough money for the petrol"?
When you go to a trackday in GT5, or any current racing game I'm aware of, you take your car and drive it until the tyres are worn and the fuel is gone. Then you pit, and they're changed. Would you rather have a menu to pop up saying "Not enough credits to change tyres to: Lexus LFA. Returning to garage" and then grinding or doing whatever to earn enough money again to pay for a frickin' set of tyres??? It'd make high-levelled racing unbearable!!!