@nerthos Sure we could. We could also put people witht he flu in prison then while they are there force them to take the treatment we want.
The notion that they "wont do it on their own" is nonsense though. Like with any disease some people get better after many attempts of treatment, some never do. Most drug addicts I know have been voluntarily in and out of rehab more times than I can count, they very clearly do treat it on their own, those treatments just also tend to fail. It doesnt help that treatment is often tens of thousands of dollars they dont have and health insurance is unlike to cure.
Here is an idea, instead of wasting an insane amount of money on sticking them in prison with worse results, why not just actually provide for them good affordable rehab on their own.