I use to think it was just about intelligent options in life, but it appears to be more than that. There is a genetic predisposition for some to become addicts. This doesn’t mean they can’t fight it or be in an environment where this doesn’t encourage this behavior, but a genetic predisposition to do this seems to be the reason.
The other thing is that some people aren’t interested in getting high for any reason, it doesn’t appeal to them. They try a drink or smoke, don’t see the whole thing as enjoyment and don’t continue it. They don’t allow social pressures to convince them this is something they must do.
Just because someone has outward success doesn’t mean they have mastered their internal success with themselves.