Earlier quoted context omitted.
As an ex-smoker, I'd ask you to consider it as about the most addictive thing going. Think of something you really, really like doing. Something that calms or pleases you every time you do it. Like, playing a game, or reading a book, or eating your favourite food. Now imagine someone telling you that you don't have to do that, it's just a choice. Imagine being deprived of it and being guilt-tripped into it. Sure you…
My father smoked for many years before quitting. I have two roommates that are smokers. The difference between him and them is that he wanted to quit, so he did. They continue to smoke because they do not want to quit. It’s as simple as that.
But even then, different people have different responses to addiction and some people find it easier than others.
Willpower is not evenly distributed across the population. Resilience to uncomfortable situations is a muscle that has to be trained, and you need that before you can tackle addiction, and keep working on it.
I'm pleased for your father, but your roommates are not the same person, and comparing them as if they are entirely equivalent is unfair to them AND your father. Your father had experience, willpower and resilience that your roommates do not yet have, and that's not their fault.
When/if you encounter addiction writ large - drugs, alcohol, gambling - the stuff that gets real crazy real quick, you might see the problem and the difficulties associated it, and the nuance of an addiction that gets at somebody that does not have immediate consequences but delayed consequences. You might then get why your father did very well, and your roommates are relatively blameless in this regard.