The harm to the people connected to the user, if you remove monetary aspects, is mostly grief about their loved one's condition. Not physical harm (usually).
OTOH I don't think addiction is an illness. It is a consequence of a poor decision which is hard to undo. Nobody is born an addict (unless your mother was a heavy addict too), and there's no addiction germ. That said, consequences of a bad decision should be treated, not criminalized. If I decide to put my legs in the wood chipper, that's a bad decision and I and my family will suffer from it. And I need medical treatment, not jail.