Many drug addicts don't actually want to be drug addicts; they started off as drug users and then lost control.

Consider if alcohol was free; would you expect alcoholics to still want to enter rehab? I think the answer is quite obviously yes. I think it's a common error of reasoning to think that illegal drugs are very different to alcohol.

You think people enter rehab because they can't get drugs? What?

Why would they need to?

To live a better life.