It's hard for the average person to know if their doctor is doing a good job until something goes wrong and it's too late.
My doctor now is excellent, he's excellent because he actually listens to what I'm saying. That doesn't mean he always agrees with me, I would hope he doesn't! But at least he is paying attention. Many other doctors seem to go into a keyword search mode when listening to patients. It's the difference between reading a page thoroughly and skim reading it.
The worst graduate in a medical class is still a Doctor somewhere...
This is probably the same feeling business guys have about engineers...
If you were on an antibiotic for strep throat, finished your course, and then asked your doctor for more of it without any symptoms, should they prescribe it again? You wouldn't cause grave harm (unless the aggregate risk of super resistant bacteria counts).
All of this shouldn't be conflated with patient centered care, though. I too agree that the patient should be in charge and the doctor should be there to support. But it shouldn't mean that doctors have to do whatever the patient asks of them.
I'm taking about stuff like modafinil, for example.