Yep, I've never smoked and have never drank alcohol.
Growing up my mom was a heavy alcoholic. She got sober and has stayed that way for 17 years now, but the sustained amount of drinking she did has had long term effects on her mental health and cognitive ability.
After she quit drinking, she started smoking. Did that until four years ago when she quit (I forced her to quit when she moved into assisted living.) She still is dealing with the effects of those years of smoking as well. Trouble walking from parking lots, coughs up phlegm constantly, all that stuff.
I have similar addictive tendencies as my mom. When I like something, I get hooked really easy and can go overboard with it. Since I know that, I just figure it best not to tempt fate.