A tenant of Free Market economies, is that a person does what is best for him. A Doctor, has long ago made the decision that he would like to help people.
Whether he makes any money on saving a persons life, is secondary to a Doctor. His only real interest is saving someones life.
This really isn't much different from any profession. You do the profession because you love it.
It's only Insurance, and Lawyers, and Government, that step in and tell you how you must treat a patient, bill a patient, interact with a patient, when things go wrong.
-John