Because by and large they don't work. And it shows a fundamental misunderstanding of the issue of stuttering and ti's giving a one size fits all approach instead of an individual one which is what stuttering is, very individual. Instead they're treating it like any other speech disorder which it is not. You can read my thoughts on intensive fluency shaping programs which extends to fluency shaping in general https://www.reddit.com/r/Stutter/comments/t2qlje/comment/hyob4u7/