I remember being interested in mods that increased the standard map sizes. But there's still a limit on the number of houses, mines, etc., so the area increases due to the density of buildings, which probably isn't always good and looks ugly.
For example, in Civ3, you can easily generate a map with 34 players and an incredibly large area in the editor, but even there, the game isn't designed for such scales – for example, it's already the 15th century, but only about 20% of the map is explored, and half of the opposing nations aren't familiar with the player. And, of course, there are bugs.