Good comment. I was going to say that while prison might work for some with addictions, it certainly does not teach them anything about staying away from drugs. In many cases recidivism is high because these people who remained sober for the duration of their sentence get out and fall right back into it within a few months. They might have trouble finding jobs due to a record, or maybe they were incarcerated long enough that they lost old, good connections or have bad ones they made while incarcerated. It might just be a matter of time until they fall back into usage as an escape mechanism.

There's just very many ways that going to prison hurts a person and very few ways that helps, and only for the right kind of people too (ex: longterm drug abuser with a lack of self control relinquishing his rights in this case).