If you think insurance companies will not find every way they can to impose the vaccine then....
Tbh I think their preference is not to pay for services. I'm not sure they see their job as to get people to go and get preventive care.
Option 1: insure unvaxxed person who gets delta, goes into ICU for a week and runs up a $400k bill, they have a $5,000 deductible...
Option 2: turn the screws on an unvaxxed, they get vaxxed and get the delta, they pay for cough medicine and a doctor visit themselves.