Left untreated is the addict's fundamental problem of his heroin addiction. Providing needles does nothing to dissuade the drug abuser from continuing to use drugs. It only makes it easier for him to do so. To leave the addict untreated does more than ensure his own misery. There are enormous societal costs involved.
Nothing is as pathetic as a sick, unemployed, long-time heroin user.
But the addict is not the only one deserving of sympathy. Just remember how many homes the average junkie has to burglarize each year to finance his habit. In addition to offering the heroin addict no help, needle exchange laws do not save the drug user from punishment and jail. Even if possession of drug paraphernalia is legalized, it still would be against the law to possess drugs such as heroin or to be under the influence of controlled dangerous substances in public. It is but a short jump in logic from needle exchange authorization to drug legalization.