The secondary money-grab is from the food-fad industry. All of the books, all of the websites, all of the memberships, all churning out recipes and advice and misinformation, depends on constant change in what's considered "good". Without constant change, their markets would dry up to a trickle. It's just like the fashion industry; if we all decided to wear the same SciFi-like jumpsuits all of the time because it's really the best thing to wear, the fashion industry would be destroyed. So instead we have a constant rotation of the fashion trends. (At least the fashion industry isn't killing us, though.)