The main reason is of exploration, both of this we call hyperspace and of the self. I've always been very interested in my own mind, how it works and how I can evolve as a person. This naturally brought me into mind-altering drugs at a pretty early stage in my life, where my introduction was composed of cannabis. From this I wandered on a wavy way with many off-paths and tried most of the more common ones, such as alcohol, stimulants, opioids of various kinds, and finally psychedelics.
Psychedelics seemed to mean something very special to me. In other drugs I only found pure recreational value (alcohol, stimulants, opioids and to some part cannabis), but in psychedelics I got very impressed to learn that there were something more to it. There was a bigger picture I just intensely urged discover more about!
I therefore in my search tried many of these kinds of drugs, such as HBW, N-Ethyl-2C-B, 2C-B, shrooms, Bromo Dragonfly, and so on. Finally I made myself an opportunity to try DMT by extracting it, and yeah, it's probably the very extreme of what I've been searching. It seems to be the most powerful tool we have to explore our minds and this (what seems to be) another realm.
It got kind of long, and a bit off the main topic, sorry! I though, find that this is a complicated question from the beginning, but I can probably narrow it down to two things; self-exploration of the own mind and general interest and belief in the positive effects of responsible psychedelic use.