That would be because it simply doesn't work. Look into official AA/NA figures and you'll find they're success rate is actually barely half the success rate of people who just quit with no support whatsoever. The whole "I am helpless to my addiction, only a higher power can save me" victim mentality of 12 Step programmes does nothing to solve any issues. In the short term there is plenty of success. See how many of those faces are still attending meetings a few months down the line. According to AA's own figures you'll find 2% still there. Cold turkey with zero support of any kind? Around 5% of such hardcore bods are still "clean" a year later. Am not a fan of 12 Step programmes aas they actively screw your chances of sobriety. They don't tend to publicise that aspect of their model much though funnily enough 8)
Anyhoo. I'd best leave it there. Suffice to say I think you are wise to be looking to other options to achieve whatever goals you have in controlling your drug use