They do perform one useful service: forcing a hospital that tries to issue a $100,000 bill that should be $10,000 to reissue it, and not leave the patient saddled with a giant debt.

(Medicaid & Medicare claims processors do the same thing. Medicaid claims processing is mostly handled by private, third-party insurers now, and seems to be able to do so more efficiently and cheaply than when it was being run directly by states; the savings is mostly in the area of catching fraud.)