I am not a neuroscientist, but I thought the actual physiological cause of addiction was similar in both nicotine and gambling: you crave the predictable release of dopamine.
If that is the (heavily simplified) case, is there a distinction for you between a chemically-induced dopamine release from smoking and, say, and a button you can press that magically releases dopamine in your brain?
I don’t gamble, but if I did, I am fairly certain it would release little to no dopamine for me, win or lose.
I don’t smoke, but if I did, I’m also fairly certain I would find it hard to stop.
You're missing the negative affect node of the Koob addiction cycle, which exists for gambling but to a lesser degree than for nicotine.