Switzerland in fact has a system very similar to what is described in this article. Methadone (and even in some cases heroin) is readily dispensed to those in need. You aren't going to end up with a 10 year sentence for possessing hard drugs, you'll be helped.
My point isn't that "countries all treat things exactly the same". My point is that the OP's alleged reasons don't really hold up once you abandon a myopic US-centric view and actually look at other countries.
But to your question, I would note that drug laws in Japan and South Korea are among the harshest in the world.
The conditions to enter those programs are rather strict. Depending on age, attempts to kick the habit and other factors.
That said. I'd say that the program is very successful for two main reasons:
It massively raises the health of the addicts and lets them actually conduct a normal life despite being addicted.
It also totally changed the image of the drug from something around hero mystique (as it had in the 80s and partially 90s) to a total loser drug. While there certainly still is a problem for a lot of addicts uptake has seriously declined.