I chalk up a whole lot of inefficiency to too many MBA's playing MD's, interfering with providers' ability to do their jobs and patients' ability to receive care, and getting paid for it.
Do you know why I enjoy caring for private pay patients more than, say, my Medicare or Medicaid patients? It has nothing to do with the patients themselves, since I love them all. It has everything to do with people who aren't health care providers meddling in health care. When I have a private pay patient, I don't have to worry about getting in trouble for providing a service that's well within my scope of practice but isn't covered. What the patient needs, the patient gets, and gets it with the least interference.
Doctors' offices and medical clinics also love what we call prompt pay, because it bypasses a whole lot of middlemen. The providers get paid better, the patients get to pay less, and nobody has to fight with a bunch of guys in business suits to give or receive the care they need.
Honestly, I think we'd be better off if we limited insurance to catastrophic coverage.