Partly because most modern day westerners are too precious to eat anything but prime cut flesh, so they're not getting the nutrients that the organs, bone marrow and blood provide. Same as my cat, it needs a ratio of these things as a carnivore to be healthy. Not that humans are carnivore, but that's a whole other argument.
The second part is the percentage of processed crap vs actual raw foods, this is what i highlighted before, is a fasting diet with junk food won't be as good as a normal diet with clean food... fasting and clean food? Just need to think of a way to turn this into a fad and become rich selling common sense to morons.