Dying people in pre-industrial cultures typically died in the context of an extended family, clan, or tribe.
The knowledge of the realm of death makes it possible for the shaman to move freely back and forth and mediate these journeys for other people.
It became much more complicated politically to work with psychedelics because of the unsupervised experimentation with psychedelics, particularly among young people.
Many instances exist of small children who seem to remember and describe their previous life in another body, another place, and with other people. These memories emerge usually shortly after these children begin to talk.
There are people who can start having very powerful experiences without taking psychedelics. It can happen against their will. This is a universal phenomenon.