Earlier quoted context omitted.
Patients and doctors need to know about a medicine to prescribe it. In order to increase brand awareness, drug companies can either advertise to or incentivize (free trips to conferences, consulting gigs) doctors to prescribe a drug or get patients to directly ask their doctor for a drug.
Few new drugs get invented each year and most are either slight modifications to existing drugs or highly specialized. Doctors can easily keep up with zero advertising needed. Drug companies advertise to convince doctors that drug X is better than it actually is. Which is obviously bad for patients who are better served by an objective approach to prescription drugs.
But I agree that doctors don't need advertisement. Just publish a technical magazine 2 to 4 times a year with a technical description of the drugs available and let the doctors make the call.