"You absolutely can insure against regularly consumed services, as long as the premium is enough to cover it"

That is called fee for service. Maybe it gets bundled with actual insurance, but it's not insurance. Regular, universal expenses are not underwritable.

Insurance is a technical term that has a strict meaning. You are absolutely correct that regular wellness checkups, etc., can positively affect the outcomes of that insurance pool, but they are not, themselves, insurable. They have to be paid for somewhere.