[snbrafford]

I worked for a BCBS company. Hospitals, doctors, pharmacies routinely would threaten to drop their acceptance around contract renewal time as a negotiation method to improve the items mentioned - payment amounts, service, payment time, etc. Few providers can afford to drop the large carriers like Humana, BCBS, or United.
Next time you get an explanation of benefits from your insurance - look at the great difference between what the provider billed and what the insurance company paid (based on contract with the provider). If you did not have insurance, you most likely would be paying what the provider billed.
Medicare drives a lot the entire process but the insurance companies stand between us and Medicare (assuming you are in a MA plan). The insurance companies are held hostage to Medicare paying their claims too in a timely manner.