Well, at a guess, it's because Xan Brooks said "Do you regret the fags and booze now that they've given you cancer?" If someone said something like that to you, would you not think it worth pointing out that a very major cause was something entirely different, that is not normally regarded as a health risk? Or would you nod and lie "ah yes, the fags and the booze, that was it, I brought it all on myself"?