You haven't seen any because you wouldn't know they're addicts. Heroin doesn't automatically take away your entire life and force you onto the street, visible to everyone. 
In fact, its effects are no different from oxycodone or hydromorphone or morphine or fentanyl .. and as we've all heard, there are loads of people getting those drugs from their doctors.
In fact, to be perfectly honest, I was on long-term high dose oxycodone for years for pain related to a chronic illness. Never stopped earning six figures in a highly creative, highly demanding professional job. Never stopped having a great marriage. Never got into a car crash, never overdosed, never stole... 
I could have been taking the equivalent dose of heroin instead with absolutely no difference to the outcome. And no, you would not have been able to tell.