At least in the U.S, we thrive on _treating_ versus curing, plus , didn't you know if you fall on hard times medically especially with anything related to addiction or mental health, you have to bootstrap yourself up from your own bootstraps or go to a 5k a week rehab facility that does not accept insurance.
If drugs are legal in the U.S, who is going to pay all those private jail/prison owners excutive salaries? Where are those corporations going to get the slave labor?
Who is going to pay all those police officers all those raises for keeping drugs off the street?
How are alcohol and tobacco companies supposed to find new consumers whose lives are ruined for possession of marijuana who are unable to secure any form of higher level of employment( extremely difficult) because they were arrested for carrying marijuana.
That's why the United States has not copied it.