Research is getting clearer and clearer on this subject. However, many try repeatedly on their own and are unsuccessful. These people can benefit from treatment.
Treatment is more successful than no treatment, but it is no magic wand.
The fellowships of NA and AA are probably not amenable to rigorous scientific study, but clearly they work for some. We are, however, a long shot away from matching patient and treatment. It amazes me how people address addiction treatment as if it is different from other disease treatments. In the course of treating my high blood pressure, I was treated with at least five different medications, with very different sites of action, before finding one that both successfully reduced my blood pressure and which I would tolerate. It only makes sense that if one treatment did not work, the goal is to try another that might because it has worked for others.