There’s a shortage of network providers because the network tends to pay peanuts, they mandate the usage of only a few treatment methods that may not be effective for the client, and make actually getting reimbursed a massive administrative headache (think many hours a week writing billing appeals instead of seeing clients). Medicaid is even worse and pays bottom of the barrel. The restrictions and complications that come with insurance repayment have lead a huge amount of providers to not bill the medical system, for simple personal economic reasons - they can’t afford to feed and house themselves if they have to deal with the lower rates and overhead of dealing with insurance.