I assume, since it's about the public, that you are talking about television ads? I think they are very much meant to get people to use whatever drug is being advertised! I believe, as I think Pachyderm hinted, that the ads are trying to increase the "base" of how many people use the drug so they are trying to blur the lines, as you say, so people who are merely "sad" might think they are depressed. Then they go to their doctor, who has no time/interest in delving further and prescribes whatever antidepressant they've asked for/seen advertised on TV.

I think, since cigarettes have been banned from TV, that psychiatric drugs should be banned from being advertised too, since they are controlled substances. Like I meant to imply, the relaxed, happy, smiling people in ads should be confined to the bladder control and low testosterone people.