I do notice that people invariably get hungry within hours of leaving a restaurant. Clearly restaurants cause hunger.

More seriously, it's not surprising that self-help doesn't produce instant results. People have widely varied and complex problems. It'll probably take a while to find the right advice, put into practice and see the desired results. Sure, there's a lot self-help gurus out there exploiting desperate people. But there's also a lot of genuinely helpful advice out there and people who benefit from it.