Personally, my distrust of the medical profession in general (I will not limit this to doctors) comes from personal experience. I've been dealing with doctors regularly since I was a very young child and it seems that the attitude is because they went to school for so long, they know my body better than I do. I have a problem with this. Case in point; while in labor with my son, I tried to tell the doctor, and the nurses that my blood sugar levels were dropping (I'm diabetic for anyone who didn't know that) and they ignored me. What's worse, they turned up the amount of insulin I was receiving! Can you imagine what happened next? When my husband finally convinced they to 1) treat the hypoglycemia and 2) stop turning up the amount of freakin' insulin I was hovering around 2.1 (I don't know what the American equivalent is, so forgive me). Needless to say, I was not pleased.
And this is just one example. I've got 25 years of stories like this (to one extent or another) that I could tell you.
Perhaps, I've been unlucky. I've only had one doctor I've actually trusted, and that was because she trusted me. She knew I am not an idiot, and I know when something doesn't feel right, or isn't as it normally should be. There are good doctors and nurses out there, I have no doubt about that, but as Trae said, far too many are treating it like an assembly line. Not everyone is a textbook case.*sigh*
I'll stop ranting now.