Paul,
You have obviously never sat in a Pro Stock Car. You can see better out of a Funny Car. The driver can't see over the scoop, or what's next to him. They sit back in the cage and have no mirrors. If the driver was sitting in the seat and a fan walked out, he would hit them before he even saw them. And if you don't think a fan would walk in front of a racecar being towed or pushed then you really don't know what happens at the races. There are many instances of golf cart damage, or straps being broken because the driver saw something and jammed the brakes, to avoid a problem, And NONE that were caused by the driver sitting on the door bar. Not one that I know of.
I was at a Houston test session one time in an empty pit pushing the car back from the top end with the driver in the seat. He hit a trash barrel that was in the middle of a wide open space with the right front. We were on the scooters pushing him and he never saw the barrel. $1800 to fix the front end.
The drivers are sitting up on the rails for one reason and one reason only SAFETY! It sure isn't more comfortable.
Alan