There are exceptions of course and I hate to generalize but often times your medical doctors are mere extensions of the pharmaceutical companies.
There is big money in SICK-care; its not health-care.
You are right, in that the pharmaceutical companies regularly call on doctors to tout their latest meds. Of course, profits are much lower when it comes to generic meds, but the shit name brand stuff they advertise on television, etc. that will cure whatever ails you regardless that you didn't even know you were sick bring in big bucks for all.
I bet there are a lot of folks who go to their doctors asking for drugs they don't really need and there are a lot of doctors who are willing to accommodate them with a prescription. Case in point, most people don't really need HRT live a healthy life and yet we get it when we whine to our doctors hard enough.