As in: "The nice fuzzy warm feeling of sitting around a fire is a side effect of self-sustaining exothermic oxidization of organic volatiles in dried wood"
Of course I made a fire for the warmth on my face / clothes. It's just the warmth I feel is a side effect of a deeper process where the heat sustains the reaction. It just so happens I'm around to harvest some of the waste heat.
If my psychiatrist gives me medicine supposed to deal with my mental health problems, I don't necessarily want contact with extradimensional entities, I want to get better.
Different purposes. Some people drink beer to get drunk, some people drink alcohol-free beer for the taste. Same with decaf coffee.
I take propecia to make sure those portals to the demon world stay _closed_
Trips without heavy hallucinations are still useful, but hallucinations without the trip? Not sure what the point of that would be.
Even SSRIs are now thought to work by inducing neuroplasticity, and they don't cause hallucinations either.