The great cop out which means that nobody has to take responsibility for their own actions, or lack of action (with regards to doing the hard work of quitting).
I smoked a pack a day for more than thirty years. Apparently nicotine is more addicting than heroin, and I was heavily addicted. But I could have stopped at any time if I had simply had the guts to do so, and had the courage to go through the withdrawal. That I didn't was not down to a disease, it was down to a lack of willpower.
And for the record, I quit cold turkey two years and seven months ago. I haven't had so much as a single drag on a cigarette since I quit. I managed to do it because I finally stopped falling for the 'addiction is a disease over which we have no control' crutch and grew the balls required to go through the withdrawal. Turns out it was so much easier than I had expected. I only wish I had grown those balls years earlier, but maybe I just wasn't ready then.
But when I was addicted I did not have a disease, I simply lacked the willpower to go through the withdrawal and to live without my little crutch. That was all it was - willpower.