Pharma reps are in the driver's seat, really. They are the ones who educate the doctors. By doing this, pharma reps are able to market their drugs effectively. So while it's not quite as direct an approach as telling someone to open up and say, "Aaah," pharma reps do have a behind-the-scenes clout in combating human illness and promoting human health.
Let's face it: Doctors are overworked and have very little time to stay on current prescription drugs. Heck, just turn on a TV for a little while, and you'll hear all about the brand-new drugs that are constantly entering the market, and each one of those represents another potential homework assignment for the good doctor. And there's lots of nitty-gritty details that they need to know about these wonder pills, like their mechanism of action (how they work), their side effects, and clinical trial statistics. And in you step, an encyclopedia of knowledge, and the docs (and ultimately their patients) will thank you for doing their homework for them.