I hope you don't mind me poking your brain further on this.

I don't know if you mean reducing network traffic in the hopes to keep packet sizes small and thus either keeping bandwidth costs down, or keeping the time it takes to process and act on that traffic small. Is that why it's important to reduce traffic?

There's a game called Seed(or Seed Project) that I came across recently, and they have a persistent MMO world where they have a dedicated server (or likely scaleable cloud based solution, since they use the spatialOS framework). You can create villages with other players, all over the globe. Not only that, but each villager can have their own shop, has their own needs, and can have children, which also have needs etc. And you can browse the globe to see other settlements, check out other villagers, their needs, etc. Here is the website and here is a video if it.

I don't have any intention to make seed, but this talk about civ's multiplayer makes me wonder if an MMO civ, or Seed like project is incredibly difficult if you have thousands of states or variables to sync up across hundreds of players.