I highly recommend "How to Change Your Mind" by Michael Pollan -- about psychedelics.

. . . a very good read :

[goodreads.com]

Much of it has to do with religion. They want a monopoly on mind control. Drugs in general and psychedelics in particular threaten to allow people new and revealing experiences which might pull them from the overloading of the church ministries. Churches draw their strength from numbers. Anything that threatens to reduce those numbers is perceived as a threat, be it Secularism, drugs or even other faiths. Imprisoning those who stray from the fold or death has always been the favored way to avoid the outflow.