...apart from in every country that does this and doesn't have lots of addicts?
It is quite strange because you go almost anywhere else in the world...no addicts, no-one uses drugs, they find it strange that anyone would use drugs...go to the US, you not only have drug addicts but a whole industry dedicated to offering very knowledgeable-sounding opinions about what should work...it never is explained why the drug problem in the US is so out of control with so many people who know what "should" work.
The only places where I have ever been that have had lots of drug addicts have been places that have tried to decriminalize (for some reason, almost always with help from the police who just want this stuff off their books altogether).
AFAIK there are drug addicts all over the world, including in the Middle East and Philippines where drug addicts are met with severe punishments. The problem is IMO more the availability of drugs vs the potential punishments people face. People are willing to take risks to do drugs. Unless a government completely controls everyone's private life there remains an ability to evade detection and take drugs while telling oneself that one will not be caught.
It's not a total solution, but a jailed addict isn't breaking into your car, robbing people at knifepoint, or resorting to prostitution to fund their habit. And they should have much more limited in access to drugs.
To help the addicts and reduce reoffending, what we probably need is better jails that are less a punishment and more an enforced rehab program with high-quality mental health support. And then a better path from jail back into society.
