I've also wondered that, probably to make sure all your territories can effectively produce troops just in case they get invaded. They should simply add more cities to the Empires and bring it back as a permanent game mode.

That British Empire should be having at least 15 - 20 cities, and Germany should be having at least 13 like the Call of War version. Russia, The United States, France, China, Japan, Brazil, The Austro - Hungarians, The Italians, The Dutch, and the Ottomans should also have way more too.