...advertising can genuinely create awareness of value adding answers.
While certainly it can, the problem is that the vast majority of time for the vast majority of people it doesn't and is consequently wasteful and annoying. I imagine that there were a small fraction of cases in which leaches were also medically effective.
Some products spread because they are so high quality. Google became a giant because its search was superb, Starbucks its experience great, and Facebook so life-enhancing.
But advertising is just a part of free enterprise. Such quick successes are the exception, and advertising can genuinely create awareness of value adding answers.