Drugs have a long history of use in magic in various cultures, and usually in the context of either ecstatic communal rituals or in personal vision quests. However compared to people in simple pastoral tribal situations most people in developed countries now live in a perpetual state of mental hyperactivity with overactive imaginations anyway, so throwing drugs in on top of this usually just leads to confusion and a further loss of focus. Plus as the real Shamans say, if you really do succeed in opening a door with a drug it will thereafter open at will and most such substances give all they will ever give on the first attempt.