The problem with that is - it requires people to either migrate away from areas that are not great at producing food without massive resource investment (or bringing it in from somewhere else), or to splinter basic things like hygiene and nutrition based on region.
For example - for the last 5 years my family has exclusively eaten locally. Either something we can produce from seed/start locally, animals harvested at our own farm (or hunted), or other items purchased from hyper-local areas (we defined this as within a comfortable bike ride from our home).
We immediately noticed that we would need vitamin supplements to make up for the lack of certain nutrients. For example - vitamin C is in short supply in the food profile in our part of the world. We didn't want to drink pine-needle tea, because it's gross, so we had to purchase supplements.
What about the people who have neither the time nor energy to devote to finding local food and/or identifying nutrition gaps in their diets? If it wasn't a hobby of mine (via low-grade prepping), we never would've known until the scurvy set in, or something else. Rickets maybe. Who knows.