that's a terrible definitioin of addiction and health. Alot of people with addictions don't think they have a problem and are unable to see it. It can affect alot of people negatively and yourself.
That just sounds like you're projecting your own values onto others for doing something more than you'd like them to. How they spend & value their time and health is their choice alone, whether it affects the individual negatively is up to their perception, not yours. The miserable drug and alcohol addicts you might be imagining are aware that it's a problem, they may not know how to fix it.
What if they had a chance to experience a life without addiction and then decide whether to live their life with or without addiction. Would they still choose addiction?
People might be happy with their life, but this doesn't mean that they wouldn't be happier with an alternative life. After they try the alternative, they could even think that what they had thought as happiness, turned out, was suffering.
But they don't, as you get older you kind of find the things you fundamentally like and dislike in life and learn to accept them, it's perhaps one of the few perks of getting older, knowing yourself, knowing what makes life enjoyable and what doesn't.