That does not seem to stop people from taking Ayahuasca, which seems to very commonly make people sick.
Most people don't even know about it or have the means to access it as its either not available or not legal in their jurisdiction so not accurate. About 45% of the adults drink. How much lower would that percentage be if alcohol was little known and subjected to the same regulations psychedelics are under?
It's the best argument to legalize them if you ask me. It's clearly a self-limiting problem - I think it's simply because of unpleasant experiences, but I suppose it's also possible that the life-changing experiences make them not need the drugs anymore.