I believe that plenty of people quit on their own. We usually don't hear about them precisely because they don't join any group or get counted as some statistic. Others can't. They need help. Not that one way is "wrong" or the other is "right." It simply depends on what works for the individual.
None of that really matters to YOU, however. What matters to you is what will you do IF he is successful? What will you do if he is not? What will you do about your life, independent of what he decides to do with his?
The feeling I get from this post is "give me hope, tell me what he is doing will work." No one can tell you if he will get sober or not. Maybe he will, maybe he won't. The question you must ask yourself is what will YOU do either way. He will do whatever he will do. What will you do?
L