Because Marijuana is a schedule one drug, and the pharmaceutical companies in the US are not allowed to even use it in drug research, let alone possess it.
That, and it cuts into the pharmaceutical industries’ opiate drug market. Opium derivatives are far more addictive than anything in Marijuana, and anybody can grow it. Pot plants vs. poppies.
Oh, on a side note, other countries markets drugs based on Marijuana derivatives specifically to stimulate appetite after chemo, and it works without all of the side effects, like getting stoned.
It could’ve been the synthetic. The oncologist just called it marijuana and joked with us about it. Either way, we got it at the pharmacy.