Providers (doctors, hospitals, labs, etc.) are not legally bound to accept any coverage types, Medicare, Medicaid, private insurance, etc.

If they wish, they can say CASH ONLY.

If you spent years in medical school, would you like someone to dictate to you what you can charge, what you can accept, what your practice should be, etc.?

If you opened a business of any kind, do you HAVE to accept credit cards? NO. Would you benefit by having more customers if you did? Probably. When businesses accept credit cards, they have to pay a percentage of the sale amount to the credit card company.

Doctors accept "coverage" from third parties as a service and convenience to their patients and to increase the number of patients attracted to their practice.

Insurance companies do not have to continue to offer the policies that are considered "grandfathered". Having a policy prior to the passage of ObamaCare (PPACA) does not guarantee that it will continue to be offered. It only means that IF the insurance company AND the policyholder make NO changes, it will be grandfathered. A change by either will void the grandfather clause.

If the provider (doc) agrees to accept Medicare, YES, he must accept the amount they pay. BUT, he is not required to accept Medicare itself. He/she may simply state that they will not accept Medicare period.