A fair point, but I was being more specific. I meant if you even look at the active principles of most drugs, they stimulate hormonal responses and perhaps dire

A fair point, but I was being more specific. I meant if you even look at the active principles of most drugs, they stimulate hormonal responses and perhaps directly things we call "satisfying". So it's not a question of naiveness or not, it's the technical question on what distinguishes satisfaction generated by a drug, by a sport or by intellectual pursuit. For example, sports practice directly releases endorphins, which as the name says, is an endogenous morphin. If they can't be fundamentally distinguished from a stimulatory point of view (my hypothesis), I'd say what distinguishes a drug to some activity we don't regard as addictive is simply that one is sustainable, leads to long term benefits while the other is unsustainable.