They're certainly more similar to each other than they are to antibiotics or chemotherapy drugs, both of which are also labelled with the term "drug".
You are mistaking noise for signal here.
> the fact that they should both be avoided for similar reasons
In no sense is this a "fact." Many people suggest LSD use. Many people regard themselves as better for having used LSD. I don't think LSD is something to be avoided at all - it's utterly benign and very, very interesting.
> They're certainly more similar to each other than they are to antibiotics or chemotherapy drugs, both of which are also labeled with the term "drug".
In which ways? LSD is dissimilar to just about anything else on the planet, and has little in common, as far as I can tell, with opioids, antibiotics, or chemotherapy drugs.
And again, let me bring up refined sugar. Sugar is a refined white powder, made by solvent extraction form plant matter, and is consumed solely for its chemical effects on the nervous system. It seems far closer to heroin than either of them are to LSD or MDMA or psilocybin. Yet these three, along with heroin, are "drugs?"
I can't imagine a consistent taxonomy which casts such a wide net on behalf of the term "drug" as to include both heroin and LSD but exclude sugar.
I take it you've never had a bad trip then?
I used to use mushrooms and LSD as a teenager and enjoyed it a lot. Until I had a bad trip, which was a truly horrible experience that at the time seemed like it would never end. I've never used any psychedelics since, and never will.
LSD is a very strong medicine, but it's possible to consume it in such a way that is profoundly helpful; what's more - it generally visits upon its users substantially less grief than heroin, to which it was being compared.
Apart from the "legal framework" what would be those "similar reasons" be?
What have you been smoking?
Heroin is several orders of magnitude more similar to antibiotics / chemotherapy drugs than LSD.