You just rock up and say, "I need something for this" and they give it to you. Otherwise a doctor prescribes it. And it's cheap.

Companies will advertise approved drugs to medical boards to be distributed down to doctors. So medical professionals decide what the best options are. There's no taking drugs just because it was on TV.

Considering Americans lag behind the developed world in life expectancy and general health, I think it's safe to say the drug industry is only there to make money and it certainly causes harm, ironically.