The difficulty stems from how much good stuff is mixed in with all the scams, making outside evaluation much harder. Most self help programs include a lot of the same basic items by necessity (fixing the big problems first). We also seem to understand implicitly that people's self judgement of the effects of these types of things is terrible, especially when those judgements are very close time-wise to the event itself (rationalization of expense and effort, unwillingness to signal disloyalty to new ingroup, even internally).