I think that's mostly because of the power of placebo and the need for people's brains to find out what really works for them. A lot of people don't feel good and have been made to not feel good by certain foods.
For example I have had a lifelong aversion to eggs, because when I grew up, the quality of the eggs was all terrible and wreaked of the sulfur from the manure of the chickens and caused me to have to hold down my meal every time I ate chicken eggs, so that now although I enjoy raw eggs, I have a natural aversion to them and if that's all I have to eat it is not likely to make me feel at ease.
I hold the belief that some foods are more healing than others within the same type of food, for instance one piece of beef may be more healing than another, depending on how the cow was raised. Both the natural forage available to the cattle and the supplements the are provided with are of great importance. Simply the inclusion of supplemental magnesium I was told had a great improvement in the flavor and quality of the farmer's beef.
I think a lot of the reason for many people's failure with a raw animal foods diet is that they actually never got to eat any actually high quality meat, we are generally only reaching 50-75% of what is possible or perhaps less.
Cattle raised on high-energy natural diets are high energy animals, with larger fat stores, healthier organs, shinier coats and higher yields of better flavored beef. I choose bison over beef when I can as I generally find the quality better however some beef I believe is as good or better than the best bison I have tried, I am certain it is more a factor of how and where the animal is raised more than anything else.
If I am looking for one thing in particular it is too feel refreshed, I feel this way by eating the purest raw foods, grown in the best high energy, electric energy means I know to raise animals. Some raw foods do it for me and others do not as much... it seems like it's becoming harder not easier to get high quality foods here in U.S.
Demand for grass fed beef is very high but lack of producers creates high market demand and lack of quality producers creates lack of quality product.
I haven't even seen a single ranch in my life that wasn't severely overgrazed, bout time I visited some.