Some of them even prefer jail. Free healthcare, three meals a day, TV and a bed to sleep in is a lot more appealing than being a homeless drug addict.
From my experience, and borrowing wisdom of others, a practicing addict or alcoholic is partly mentally ill. Some say insane.
A man once said "you can't fix a broken brain with a broken brain."
AA's 2nd step includes this: "...restore us to sanity." Elsewhere in AA literature reference is made to "...a moment of clarity."
All of that follows the belief it goes beyond "willpower" and "healthy decisions" etc. The people that do NOT become addicts and alcoholics have those powers intact.
The addict and alcoholic needs help from a higher power, of their own understanding. Many call that power God.
A happy sober life awaits, in place of dependency on substances--for those willing to take the risk of trying.
Back to krokodil--the damage is visible on the outside. Same for rotted teeth and scabs from meth. For other substances, the damage may be invisible, even spiritual in nature.
What about the elderly addicted to pain killers? Trapped, powerless. I have recently gained empathy for them, taking them because they are addicted long beyond the underlying pain issue.
These people look normal, not tatted up addicts, or smelly alcoholics falling down. Maybe your Mom or grandmother.
Gonna lock them up?