Consumers who care enough about the medicine they’re taking to request certain prescriptions want to understand them. Mass media like TV ads drives searches and visits to more detailed official material (websites, pamphlets, etc.) Without providing useful information, the manufacturer would have trouble convincing more engaged patients to switch, and similarly to other product markets, engaged customer word of mouth is vital to growth. Word of mouth is bolstered by the more familiar mass media. It’s not perfect, but it’s far from axiomatic that the communications from the entire marketing campaign are valueless. It only appears that way to TV viewers with no medicinal motivation to research the drug.