The government already does this via Medicare/caid. They are considered the gold standard of reimbursement for insurance companies and hospitals. Medicare/caid's guidelines on what they will and will not pay for are very clear and they stand by their rulings.

Insurance companies, on the other hand, will break their own agreements left and right. One major health insurance company in the US has an internal policy of blanket denials of claims. Meaning, if you have them as an insurance provider, it's about as effective as having no insurance. Unfortunately I can't name names.