Or are you saying that drug treatment is "good" because it keeps people out of jail? (ie., given a choice, who wouldn't take the treatment program?)
"Assuming you were arrested and assigned to a drug treatment program -- would it do you, personally, any good? Are you addicted to marijuana? Do you need treatment?"
Are you addicted to caffiene? If you were arrested and assigned to a drug treatment program for caffiene abusers would you do it?
What I am trying to say is that, in the case of non-violent (or rather all other things equal) drug use or drug dealing, the punishment (prison) does not even come close to fitting the crime. The amount of harm done to society is rather low.
Think about it. What is the harm of one person doing drugs in thier home? I understand they are harming themselves, but we don't put people in prison for a whole slew of things we could do to hurt ourselves in our own homes.
Now, if they drive or some such other thing whilst under the influence, then you have a case, otherwise, leave them alone.