Treatments like exercise also have high variance - depending on the circumstance and how diligently you implement it, it may have no effect, a big effect, or even cause injury in the worst case.

Insurance likes low variance outcomes because they’re easier to model accurately

I’m not in the insurance industry and have no idea what the actual reason is.

And I don’t know what the statistics are, but a significant percentage of people with gym memberships rarely go to the gym. I suspect the percentage of people with free (i.e. payed for by insurance) insurance who rarely go would be much higher.

Further thought: Maybe insurance companies could pay, reimburse, or reduce rates for those who can reliably prove they are exercising.

My insurance offers reduction if you pass a basic health check each year. It's kinda nice but also sets up a slightly adversarial relationship with my doctor, which I don't like.

Ideally the health checks would be done with someone else, to reduce that adversarial conflict of interest problem.

Maybe your doctor should even get a small reward each time you pass the basic health check, so that in aggregate they are better aligned with keeping people in shape for those checks.

I've seen plans that subsidize gym memberships.

>health insurance doesn't cover gym memberships or exercise equipment

Because neither of those things are necessary to exercise.

I bet if you asked your GP for some body weight exercises you could do at home he'd happily provide some for you and insurance would cover the visit.