It wasn't always this way. I had to look up to see when exactly it started. A couple answers I found were:

"No federal law has ever banned DTC advertising. Until the mid-1980s, drug companies gave information about prescription drugs only to doctors and pharmacists."

"Direct-to-consumer advertising of drugs has been legal in the USA since 1985, but only really took off in 1997 when the Food and Drug Administration (FDA) eased up on a rule obliging companies to offer a detailed list of side-effects in their infomercials (long format television commercials)."

So yeah, I remember well when you would never see such ads. I also remember how outraged I was upon first seeing them. My opinion really hasn't changed. It's idiotic.

Apparently, only we (US) and New Zealand allow direct-to-consumer Rx drug advertising.