If the nurse has an issue with nursing care, in contrast to medical care, they aren't going to call the physician for orders. Additionally, they aren't going to call just because they're scared about liability. Personally, I think the "I'm not sure if the patient who's A/Ox4 and has capacity can sign AMA, so I'm going to call medical control just in case, and that way the liability is on them" type of call is nothing more than a -false- sense of security.
I don't want to have physicians riding on every ambulance. I want the people who are providing care on an ambulance to be able to have the foundation to make decisions and justify those decisions without using medical control as a "I'm scared of the dark, and medical control is my blanky."
Furthermore, it's not even appropraite to compare a nurse calling for orders to a paramedic. The ward nurse more often than not is calling the patient's personal physician, who personally knows the patient, has examined the patient, and knows what the patient's current treatment plan is and why, where the medical control physician only knows what the paramedic thinks is important to tell him.
Oh, and if EMTs aren't professionals, then they need not be on an ambulance without direct supervision. If paramedics are a profession, then they, as a whole, need to start acting like it, including demanding a proper education.