50% of alcoholics stop drinking on their own without any help. So the people in AA, SMART Recovery etc are the "tough nuts" to start with. This makes the numbers lower to begin with. Also this high "failure" rate isn't the end all. Many people don't get sober after attending one or more meetings. They may still be contemplating whether they even have a problem. Think of how many times we've seen these folks in the rooms, and later come back and become sober.
That was me. I first went to a few meetings and then waited five years before really giving the program a good try because I had a problem and didn't want to live with booze in my life any longer. So technically I am under that failure rate. Someone better tell this to the enamel coin I carry around in my wallet.