I suspect the reasons these games don't are twofold: firstly it's difficult technically to get an engine to deal with such large scales effectively, and secondl

I suspect the reasons these games don't are twofold: firstly it's difficult technically to get an engine to deal with such large scales effectively, and secondly it's hard to make the gameplay work around such differences. (That said, EVE has had realistic scales for space for a while, and star citizen is boasting about their engine which can handle such scales, though whether that will actually turn into a game is yet to be seen)