It's not about being informed, it's - like all marketing - about being misinformed. And in this case, the intended effect is that the patient will pressure the doctor to prescribe them the drug they've seen on TV.

I don't think prescription drug advertisements are a good thing, but it seems to me the real problem is doctors that allow themselves to be pressured.

Which is why it is illegal to market prescription medicine to consumers.

Not in the US, of course.