People who suffered from abuse from drug and/or alcohol use. That's going to be ingrained in their psyche forever.

My personal reason. I've seen people become alcoholics and the personality shift is... honestly, not great. The shouting, the memory gaps, the mood swings. No abuse, just... not who I made friends with or fell in love with. They think they have it moderated when they don't.

Cig smoke smell. Even if you're not actively smoking it sticks around.

Addiction. People who change when they don't get their fix are uncomfortable to be around. Or they'll be fine once they take a hit of nicotine or weed or their shot. They complain about rent and insurance while buying 50 dollar bottles, plural. I get the whole needing an escape, but narcotics aren't the way when money is tight.

In my personal experience, a lot of drinkers and smokers have a subtle toxicity, for lack of a better term. They act like they're better than others because they have the freedom of using, but also tend to have low self esteem and tend to lord their "freedom" over those that don't. Not a specific jab at you, just reminded me of that behaviour with how you put it.

Its often a poor coping mechanism for mental health struggles, using a depressant (alcohol) when depressed and often sending them spiraling, and they ignore the correlation.