they don't? it's a multi-million dollar industry that sells non-information to people; some of these people so stupid that they ingest it as factual gospel and use it to run their lives.

I'm not against it, but it doesn't take a lot of mental gymnastics to see the harmful aspects of horoscopes. The victimization of Andy Kaufman and Steve Jobs using psychic quackery, although different than a horoscope, comes to mind right away -- it's just not that safe an idea to sell confidence in quackery.