(I'm fairly new to Civ, so forgive me if I'm a total noob
)
I've noticed in several screenshots today that many civilizations have unimproved spaces within their territory, even in late game.
Every time I play, I fill every tile under my control with something. Farms, mines, trading posts, lumber mills, etc. Is there some sort of advantage to not doing this?
If anyone can clear this up for me, that'd be greatly appreciated.

I've noticed in several screenshots today that many civilizations have unimproved spaces within their territory, even in late game.
Every time I play, I fill every tile under my control with something. Farms, mines, trading posts, lumber mills, etc. Is there some sort of advantage to not doing this?
If anyone can clear this up for me, that'd be greatly appreciated.