...and the chance that your normal auto insurance will pay for damage to your car on a racing surface- 1:10,000,000

While you maybe be less likely to have a fender bender on your way to work, you chances for significant damage are much higher on a track. In other words, you're more likely to go off roading at a track event than on the street, going off roading means you could hit something hard and do big damage. Driving on the street you're likely to have someone hit you in a parking lot or at a traffic light not paying attention.

I think it's smart to get the insurance if you have the money...the price you paid is usually for the whole weekend...right?