It can trigger deep psychosis which can take people years to come back from, or even permanently 'break' personalities and make people worse human beings. Imagine having very dark bad trip for the first time, on high dose, with nobody around to help.

My opinion is that those people could end up there via different ways (alcoholism, mental shocks like car crash or other mental traumas), but this is definitely one way.

It is extremely powerful substance and can take you very far from common reality, not something most folks are prepared for. I know I was not, and having every single aspect that makes me me taken away, both on physical and personality level was by huge margin the most intense experience of my life.

I believe it should be legal (maybe with some huge warnings/education about potential consequences), but from all I've heard LSD is just synthetic variant of the same - why would that be illegal then? If that is OK, what about mescaline, that's also just a plant? Ayahusca? Cocaine is also a plant extract, and so is heroine (with some chemistry on top of that, but coca itself has quite an effect on its own). A bit slippery slope...