It's not even about the relative risk of being on track or your driving ability attitude, third parties, or relative likelihood of encountering fluid spills. The question is simply, "I'm thinking of gambling my car value of X to win insurance cost of Y at Z number of trackdays, should I?".
If your car value is £1,000 and insurance is £50 and you're doing 10 days a year, probably not. If it's £10,000 and you're doing 3, who the hell stakes £10,000 to win £100??? That's the world's crapest bet, whatever the odds