I don't smoke, but I do drink alcohol in moderated amounts, and I'd disagree that alcohol is "killing us" [1], and feel that even if it were proved beyond a doubt that alcohol monotonically decreases lifespan, it helps make life enjoyable enough to be worth it. The same is true for processed sugar, in moderate amounts (though I'd take a ripe honeycrisp apple over a twinkie any day).
[1]http://www.wired.co.uk/news/archive/2010-09/09/why-alcohol-i...