"In a society in which drug use is more tolerated, it seems likely that those seeking to get off the junk would be lower."
I doubt people like being junkies any more in the Netherlands than they do here. That would be a miserable life regardless of the laws. I think the fear of arrest and incarceration is low on the list of worries for drug addicts here. They're much more concerned about how they'll get high tonight, if they are going to eat, where they'll sleep, and that sort of thing. The threat of getting busted is just one more thing they put out of their minds.