I usually take it out, although I will always drive within the limits of myself and the car, 1. mis takes can happen, 2. as zmanalex said, fluids are a big issue, on monday a oil burner diesel dropped diesel all around the same corner chris went off, I know as i was behind it when it was covering my car 3. Mechanical failures, Someone on here had a top mount break at high speed, I had a brake hose burst in july @ 130mph towards paddock hill. There are so many things other than your own driving skill that can cause an accident on track
Buy insurance unless you can afford to replace your car when you track it