gotten anything back.

The system is what facilitates this.
You get work done, and don't know if it will be paid for. The service entity submits an inflated claim knowing that the insurance company will decline to pay part of it. The inflated claim is because they feel that their services will be undervalued and underpaid by the insurance company, so they inflate the claim and hope that they will get what they fell the service is really worth. The actual customer is okay with it since they have been paying for coverage all these years and feel like they should be taken care of. The customer is okay with the service company submitting an inflated claim if is gets the insurance company to pay enough for the service so that the service company doesn't try and come back to the customer for additional payment. Their mentality is 'do what you need to just make sure that I don't have to deal with this.'

Kind of a vicious circle where everyone feels like they are going to get hosed and feels like the others are the crooked ones, not them.