It was to give people whose mental health had been improved by psychedelics long enough to turn back into crazy cult fodder. :-)
http://www.popsci.com/science/article/2013-08/psychedelics-dont-give-you\ -mental-health-problems-study-says?src=SOC&dom=tw <http://www.popsci.com/science/article/2013-08/psychedelics-dont-give-yo\ u-mental-health-problems-study-says?src=SOC&dom=tw>