I can see what led you to confusion. Let me make an example.
If you get a game with the entire US map, every city, town, street.... that would be big right? Now, in your ingame map, I put a map of the whole world. But you can just play on the US. You would say, wth, I heard this game has a whole map but I can only play in a 15% of it!!!
That's what is happening here. The game where you can play is HUGE. But since you are seeing also the rest of the world where you can't go, you are asuming it is only "a few" zones.