@SteveJust Because of culture, wealth and maybe freak coincidences.
Notice how most western vegetables end up as salad while the Chinese have more fried vegetables
. Meanwhile the Indians somehow managed to get their spinach dish to end up like a sauce
.
More extreme examples would be casu marzu (also known as maggot cheese) which probably started off as an incident and kopi luwak, which is created appparently because some poor people REALLY WANTED to try the then new thing called coffee and decided to use partially digested coffee beans since they can't get their hands on fresh coffee beans.
Based on this particular nomadic Elven culture. Each tribe has a 'specialty'. For the MC's tribe, it was milk. The merchant guys have bread and the wedding guys have tomato. These are the only "edible" things because they are produced. They have an abundance. Things like meat and vegetables on the other hand are more scarce.
Also
the people who waste food gets the axe. This is likely because they don't actually have enough food variety for a balanced diet. (e.g Not enough carrots. Can't experiment on carrots.) As a result, there is not much of an incentive to experiment with food.
As for the things they have an abundance of, they probably ended shifting to the mindset of not trying to fix something thats not broken.