1. This assumes it’s impossible to disincentivize drug usage via really harsh penalties enforced by state power. But look at China, where they have very little drug usage, due to extremely harsh penalties, and extreme social stigma. Individuals don’t get “mind expanding” or therapeutic benefits of drugs, but at least the society is not paying the cost of externalities of drug usage (see San Francisco’s Tenderloin).
2. Not all who do drugs are rational individuals with full information about what might happen if a chemical dependency is established. There are people pressured into drug usage by both legal mechanisms (Purdue Pharma) and illegal mechanisms (e.g a pimp creating a prostitute by forcing a drug addiction on that person). So the implication that there’s no bad actors, and it’s just the state enforcing draconian measures, misses very real cases of bad actors who should be stopped and punished. A legal system that pursues and removes bad actors can help society.