I wouldn't say "most"....but that's just me.
Of course, you are right.
I just don’t think it hurts to be skeptical and question the motives of people who stand to gain financially based on what they recommend — in any field.
Obviously, the reason you hire a doctor is because he or she is supposed to be an expert, and you want an expert opinion. I am not even saying that “most” doctors are not good people. Money can talk loud.