I appreciate your anecdote. I have no experience with heroin, but I imagine softer drugs with relatively mild or non existent withdrawal symptoms carry the kind of addiction kind you can grow out of. Say, pot, or various amphetamines.
There's also got to be some kind of chemical/medical aspect to how a certain substance affects you individually, apart from how it affects everyone else. I was more of a cafeteria drug user and got bored really quickly and the only objective was to be high(or low), not necessarily an obsession with one kind of drug. For instance, heroin withdrawals were never stereotypical for me. I'd always thought of it as a high wearing off, and would fix it with any other drug that was available, it didn't strictly have to be heroin.