"no possible health benefit with smoking"...as usual, it's more complicated.
See, for example,
http://aje.oxfordjournals.org/content/155/8/732.full
for the negative correlation between smoking and Parkinson's disease, and
http://ajcn.nutrition.org/content/87/4/801.full
for some insights into the negative correlation between smoking and obesity.
Not to say that smoking is a good idea, it's not (actuarial data are clear on that), but your view of its consequences is inaccurate.