I think you missed one important part - how addiction is often about not doing something else. Addictive games are easy to set up and play and you can do them at any time. I can play an online flash game at work (well, i think I could, I haven't tried yet.), but I can't just sit down with my friends to play D&D.
My point is about D&D's systemic design and the nature of the systemic gameplay it promotes. The notion that a tabletop environment is different than a virtual environment is irrelevant to my point. I am focusing on the game system: two tabletop rpgs with different systems are different in the way rules guide player decision making, even if both are tabletop games. I am talking about a quality value, that maybe its effect is different in tabletop rpgs than crpgs but nevertheless it still exist up to a certain point.