Why not? Ketamine is commonly used as topical analgesic, for example, when applying sutures.
Injected, it causes hallucinations and memory loss.
It can be pretty nasty stuff.
Ketamine and eskatamine show very promising results as treatments for depression, at sort of mid-dose range. In fact, a person I know very well is working on getting a referral right now
What to you mean why not? Ketamine is a totally different class of drug than lsd/mushrooms.
But, yes, you have a point if it is only placebo effect.