Yes you can get cheaper premiums by living healthy, but how far do you want to go? Are you going to let your insurance company log everything you eat and how many steps you walk every day? Seems much easier to just factor in the external cost of goods into their price.
For medical insurance, it seems they could at least do something like "if you send us evidence of healthy exercise/diet/weight, then we'll lower your premiums; otherwise you'll get a premium based on the estimated risk of the set of people who don't do this". (If the government doesn't forbid it. healthcare.gov says "They also can’t take your current health or medical history into account", which sounds like it might rule out some of that.)
1. It was probably a tax write off.
2. It was probably also both a community service project AND a reflection of lower expected insurance payout.
3. Maybe the straight-A students are correlated with insurance payers that would rather pay the repair known 1-off payment (or skip doing anything at all) vs the unknown recurring increase in insurance payments?
(Source: drove a dented-up pickup for over a year after a short romp along/into an orchard)
2. The lower expected payout is exactly what an insurance company is trying to determine, and they’re very good at doing that assuming they have lots of data.
3. Most vehicle insurance cost are liability related, meaning the damage their insured to others, and namely healthcare costs. A collision with another person or their property will not be fixed without the insurance company getting involved, and a reduction in those is what the insurance company is betting on.