UnitedHealthcare suggested in a comment to Newsweek that it did not call Potter during surgery, saying, "There are no insurance related circumstances that would require a physician to step out of surgery and it would create potential safety risks if they were to do so. We did not ask nor would ever expect a physician to interrupt patient care to answer a call and we will be following up with the provider and hospital to understand why these unorthodox actions were taken."

Maybe UHC just needs to read the article they are quoted in to get the answer:

In a follow-up video, Potter said on Wednesday that insurance companies have created "a fear-based system where, if an insurance company calls me and says I've got to call them right back, I'm afraid they're not going to pay for my patient's surgery, that patient is going to get stuck with a bill."

So the answer is: Doctors and patients are so afraid of doing anything that might be an excuse to let UHC deny covering the healthcare procedures. This fear isn't manufactured by doctors or patients. Its a direct result of UHCs prior actions.