It's important to note that when people talk about drug abuse and its impacts, they are usually referring to heroin and opioids, amphetamines, cocaine and other alkaloids, benzodiazepines, and so on. While some of those drugs are hallucinogenics, none of them are considered psychedelics, which is what the current decriminalization conversation is about.
Magic mushrooms, LSD, and cannabis are in a different universe psychiatrically, addictively, and experientially. It's like comparing viagra to chemotherapy: yeah, a blood thinner carries extra risks for certain subpopulations, but chemotherapy has visibly destructive side effects on the entire population.
Because when Portugal decriminalized every drug, the country saw an increase in drug use that was the same as the increase in other countries that didn't decriminalize [1]
Oh look, it's the gateway-drug argument [0] all over again.
The short version is that, for those other drugs that the grandparent listed in their comment, they are already scheduled for medical usage. Only the psychedelics are scheduled away from any legal usage.
Magic mushrooms, LSD, and cannabis are in a different universe psychiatrically, addictively, and experientially. It's like comparing viagra to chemotherapy: yeah, a blood thinner carries extra risks for certain subpopulations, but chemotherapy has visibly destructive side effects on the entire population.