That suggests that insurance companies write, practically literally, hospital rule books.
How much deeper into a doctor's practice does that get? (My recent experience has been that unless they're pushed to the wall, doctors won't even answer questions. [Does that suggest that they're simply careful... or actually vulnerable?])
You broke the code! Doctors are vulnerable for what they say and often have little they can say with certainty because there are so many non-medical constraints on how they practice medicine.
The liability and malpractice insurers dictate the informal and formal policies in the hospital and force the practice of defensive medicine. The third party payers (health insurance providers) control what diagnostic and treatment procedures as well as treatment regimens by what they will pay for and how much they will pay for it.
