As a medical student I was taught that addiction is a spectrum. Each drug falls somewhere on that spectrum in terms of addiction potential, (And as GotAnyMegadeth comments, Nicotine is more addictive than Heroin) and every person has some prior probability of becoming addicted, due to the complex interplay of social/biological factors that go into the nature of an addiction).
Okay - so Heroin is less addictive than Nicotine. We know this. People understand this if they think about the nature of addiction. Doctors are taught this at medical school. Community mental health, nurses and doctors talk to lots of people who have tried hard drugs and never got into them.
But what is the destructive potential of trying heroin and becoming addicted? Obviously much greater than with nicotine (Although nicotine products may well result in your death one day too).
This information isn't particularly new, and certainly hasn't been buried by the powers that be in an attempt to strengthen anti-drugs arguments (at least in Australia)