Doctors and their staffs can see (maybe even smell) pharmaceutical sales people from several hundred yards away. Drug reps look the same. Women wear tailored, black, wool business suits with white blouses. Men show up in black gabardine slacks and blue shirts, usually with apathetically chosen neckties.
Receptionists apply their prejudices as soon as a drug rep walks through the door he or she just held open for woman pushing a stroller. And those prejudices, good or bad, control the drug rep's upcoming experience. Perhaps there is a set of office rules governing which ones or how many the doctor will bear to see in any given day, but mostly, it is the first impression of the person guarding the door that will determine the success or failure of the predestined sales rep.
So why do they all look the same? Because same is comfortable and familiar. If they do things the same as all the others they will be accepted into offices, they will deliver predictable results, and they will keep their job. When they look like everyone else, they know there are no mistakes being made. Except, of course, the most gigantic mistake of all - the absence of an original idea.
Would a woman in a red suit or a man in carefully selected tie really shake up the status quo? No. But someone dressed up like an average patient or another medical professional might. At least it would provide a fighting chance to overcome the prejudices leveraged against them, forged by the uninventive masses which came before.
Looking and sounding like your competitors has been proven to fail. Being original, on the other hand, only fails some of the time.