I'm unsure what you're meaning by needle share, maybe the risky behavior some IV addicts do where they share needles? There's controversial programs in some liberal cities where addicts can exchange needles for new, sterile one, or just get new ones.

I think it makes sense though. You often can't change an addicts mind about using, and if they do change then it's very often something that has to come from within themselves. Giving new needles helps reduce some harm in the long term by reducing transmission of diseases and not having more cases to take care of in the healthcare system. It keeps them healthy longer in case they're able to get help and get clean at least at some point. It gets them into regular contact with people who can help get them into addiction programs if they're willing. I think those are all very positive things when trying to address the drug problem and taking care of people too.