One of the points they make in the book is the both treated and untreated addicts recover at the the same rates, in fact the untreated recover at a slightly higher rate. What they ask in the book, and I quote,
"What would you conclude if you took a group of people with a disease, and gave some of them medical treatment and the others no treatment, yet both groups recovered equally? You'd have to conclude that both groups resolved their own problems by their own power. You'd conclude that the treatment doesn't really work. And if it doesn't work, then it certainly isn't "needed."
It's not the first time that I've read that most people get better, no matter if they seek treatment or not. I think the idea is that once a person decides to go to treatment they've already decided to quit and the treatment is because they believe they need it, when all they needed was to decide to quit.