This is never taught properly in textbooks for a variety of reasons. For starters people don't want to give up their personal bias, their cultural customs, and they definitely don't want full responsibility for their good and bad decisions etc...
Furthermore, schools don't want to take a hard line on subjects like this because there will always be people by the hundreds of millions incapable of, and unwilling to be objective, unemotional and accept the facts in this department. Not only is the subject of diet highly emotional (a very odd phenomenon where people's identity becomes what they eat or don't eat) alienating that many people is flat out bad for business.
Emotions aside, there is an unseen web in the big publishing world controlling the information gatekeepers of the system are exposed to. They don't want the truth getting out, they don't want objective, unemotional, definitive facts on nutrition based on Anatomical design becoming mainstream and uncontested because then people would be impossible to control. If the objective truth about diet was out and followed, both supplement and drug companies would take a huge hit to their profits and therefore have a vested interest in confusion remaining the status quo.
The reason it works and nobody seems to care or notice, including amongst grads of these programs? There are 3 primary reasons:
1) They don't want responsibility all that much more then the general public, as nobody wants to live perfectly or be held to that standard.
2) Subjects are taught in Silo's in school so the dots never get connected
3) The education system rewards, regurgitation without question, not independent thought and it tends to attract people accordingly.
Don't get me wrong there are many nice, intelligent people with great intentions that graduate from all the above, many of whom I call friends. This is not personal and I suspect there are many humble enough to tell you about the shortcomings of formal education and credentials.
If you doubt the education system is flawed across the board allow me to teach the remainder of this article in pictures using common sense.
Some Dr's say this is healthier than.... This?
Some "Experts" believe he should be doing this instead...
Some "Experts" believe you can skip diet and just eat pills, potions, tinctures and lotions. They only debate whether or not it should have come from a lab or Nature.
If textbooks were teaching things properly could the diversity of opinions so wildly across the spectrum even be possible? Of course not! Take the pills out of the equation and justify while remaining objective, and logically consistent how this mess (which came from the pot of bones humans are both unwilling and incapable of eating above) be superior to fruit which is constantly vilified. Gag!
I want to keep this article short but suffice to say fruits and vegetables are the health foods for humans, it wasn't the other Primates that read the wrong textbooks. Textbooks are wrong all the time, nature never is. Without going into the history of humans, from a digestive anatomy standpoint we are identical to the other Primates and I promise you they are not the ones who are confused. Despite every ridiculous logical fallacy ever invented to justify what someone wants to be true about diet, and trust me I've heard them ALL so please spare me. Facts don't cease to be facts. There is nothing more first principle oriented than comparing food sources against digestive anatomy, cultural arguments can't even be regarded in the same league from an objective viewpoint.
I know, I know, but but but but....is on the way.
You would never eat raw bone marrow or raw chicken feet nor do you have the teeth to do so, and the Quintessential Carnivore is in danger from and gets ill if they consume cooked meat/bones but you personally are different, eyes rolling. Your ancestors used to cook them down for the goopy mess and a few very confused "Experts" on the internet told you that bone broth is good for you AND you like it therefore it's health food. No logical fallacy to see here at all.
If you want to learn Nutrition properly find experts who are unemotional, objective, logically consistent, honor and parallel nature but also contrast their viewpoints with science. Some of the best books on diet I've read contend that herbs and many other plants are toxic to humans despite having thousands of studies stating the contrary. Objectively the best one can say is they are not "optimal/natural" food sources but one can't state they are unhealthy in the face of evidence to the contrary.
For those conjuring up Omnivore and Carnivore arguments despite completely lacking in Anatomy suitable for the task....wait did you hear it? Is that Steven Tyler I hear singing Dream on, dream on, DREAM ON....................
Be objective and decide what you will live with from there.