I agree that rehab is not always the best solution, because it does not teach the user to wilingly bot use drugs, just forces them not too.
You can't just group all "hard" (what exactly does this mean anyway? Is diamorphine "hard" but morphine not? Codeine? Tramadol?) drugs under one umbrella. You ESPECIALLY need the appreciate the differences between, for example, benzodiazepine (are these "hard"?) withdrawals and crack withdrawals. An addict withdrawing from crack/coke mainly needs sleep and nourishment, "cold Turkey" is a realistic option. An addict who is physically dependent on benzodiazepines will have a grand mal seizure and die if you attempted to force them to "cold Turkey". Gabaergic withdrawal (alcohol/ benzodiazepines/barbiturates/GHB) is a death sentence, opioid withdrawal (diamorphine/morphine/ methadone) sincerely feels like a death sentence but is very rarely lethal (and then almost always a result of dehydration), stimulant withdrawal (meth/coke) is never lethal. I've oversimplified greatly, but I think you get the point.
Also note how alcohol withdrawals are often lethal. Very few people classify alcohol as a "hard" drug comparable in seriousness to heroin, but from a physiological perspective alone, alcohol dependency is far more damaging to the user than heroin dependency. A dependent user could use opioids every day of their life and die at a normal age, completely healthy (the negative health effects from opioids are almost entirely a result of users being forced to turn to a black market). This cannot be said for alcohol.
Before advocating for any policy in regards to a serious public health issue, please at minimum read up on the literature regarding physical drug dependency, the differences between the major classes of commonly abused drugs, and which (humane) approaches other countries have tried which have yielded positive results.
The problem of wanting to "cure" addiction by using drastic measures like cold turkey or rehab is that it may not be the best course of action. Perhaps it is better for many people to acknowledge that the addiction is in fact "just a phase", and that a proper way of dealing with it would be to accompany the addiction so that the person wouldn't be harmful to himself and others, until the person reaches the point where they "outgrow" it naturally.