I don't read the advice as "remove all your support framework, friends, and family and go at it alone". I read it as "find supportive people who can enable your goal".

For me, it's absolutely trivial to not drink or not smoke in groups of friends. But that's because I'm NOT a drinker and I'm not a smoker.

For anybody I know who IS a drinker or a smoker, casual or hard-core, the social aspect is absolutely pervasive and can be brutal in trying to quit. If one is not a drinker or smoker they may have a hard time fully empathizing / understanding how hard it can be to be around others who not only partake, but see it as critical focal part of activities.