Though I don't have any stats ready on how many heroin users end up as addicts that actually hurt their health, and how many recover later, you don't seem to have it either. Before we have some kind of numbers, I don't think discussing this can lead anywhere constructive.
I'm pretty sure that most users of nicotine (as smoked tobacco or in electronic cigarettes) get physiologically addicted pretty quickly, and in a pretty hard way. Though this is inconvenient to them, it usually does not bother people around, because nicotine is not a behavior-altering substance (unlike alcohol or cocaine). AFAIK, heroin is not a behavior-altering substance either. It's the lack of a dose what dangerously alters the behavior of a heroine addict (or an alcohol addict).
Since heroin is outlawed, users have far lower thresholds to pass to act unlawfully in other regards, since they feel like criminals already. A heavy nicotine addict may suffer immensely without a fix, but usually stays a lawful citizen despite it.
Take insulin: it's also intended to be used as a drug, and improper use can quickly kill you. Thats why it's a prescription-only substance, but a completely lawful one. Quite a few over-the-counter drugs can kill you, or at least severely cripple you, if used improperly. Do you think outlawing them is a good idea? (Hell, 3/4 pound of table salt, if ingested quickly, would kill you. I hope you exercise reason when adding salt to your food.)