I think you may be confusing life insurance companies with health insurance companies.
I am unaware of any health insurance companies viewing tobacco usage as a preexisting condition, but many offer healthy lifestyle coaching and advice as well as discounts on gyms, weight watchers, etc.
My particular insurance company likes to have a "nurse" call me every-so-often to check on my wellbeing and make sure that I'm eating all my green vegetables and that my diabetes is in check (even though they can't do anything about the contradictory coverage policies that the company they represent has). Still makes me feel all warm and fuzzy though.