I once was lucky enough to have my primary care physician through a university teaching hospital that outsourced almost nothing. Billing was in-house, insurance ops and claims processing was in-house. Labs went to an accredited in-house reference laboratory.
I am sure it was easy to justify doing everything in-house because the university held accredited degree programs for virtually every healthcare area from medical school to ophthalmology and optometry, physical therapy, pathology, dentistry, a college of nursing, pharmacy school, as well as specialties like oncology, cardiology, and anesthesiology. For the areas that weren't medical disciplines, they operated degree programs for bioinformatics, hospitality (the hospital cafeteria was excellent), and several other areas that just so happened to address essentially all the needs of a modern healthcare organization.
It was a fantastic model, but it might have only made sense in the context of a large teaching hospital.