In general, one of the factors that all civs have in common is an influence bonus, which is that “some” building generates a gridded area, and affected nearby buildings generate a bonus to them. Aesthetically, it makes sense to force the player to better organize their cities in a way that they take better advantage of the bonuses, as well as to give the cities certain distinctive characteristics.
Not to be confused with aura affecting units, area of influence only affects buildings and in a grid pattern. For some reason the Corral Fulani Landmark Mali does not use grids, but a circular area, I don’t know if it is related to the fact that it is the cows that collect food from their corrals, or they did it like this to avoid being confused with the influence of Communities mining.
I would give examples, but CRothlisberger already put them, good job by the way.
Just in case, most of the info can be found at aoe4world. My grettings.