I think there are many factors... I really believe that some people have different needs than others, some people do well with a lot of carbs, and some people manage with a lot of proteins, and some people don't.
Paleo has a lot of advantages, but too much nuts and seeds can be a problem for many.
And allergies are seen are something like "an exception", when actually there are so many of us who suffer from the same allergies. All these people who have gluten allergies or nut allergies, it's not just "bad luck", but different metabolisms and needs.
But in general, in the west nowadays, food is very much based on gluten/grains and dairy, and theses 2 are often bad for teeth. Paleo is what many living in west need now... I think we maybe have different needs depending on what kind of diet we've had in the past. If you've been a raw vegan for some time, chances are you need some meat/animal products for you teeth. If you were a huge meat eater, more greens would be beneficial.
Fruits are sometimes seen as bad, but if we have a balanced diet, they are a very wholesome food giving a lot of energy. We need variety of different food to find the right balance, and listen to our needs.