But couldn't they put one functioning fort out of all the forts in Cyrodiil?
They should have, but they didn't (except Battlehorn but that is a DLC, and even that fort was being invaded by Mauraders), it's pretty much a shame they didn't, I believe there were modding plans for the not quest related forts, to make them liveable again, ofcourse I understand a couple of forts (specially the far away), can be ruins, but the forts along the roads and towns shouldn't been ruins at all ...
The seem counts for Mines, it's so far unlogical that all mines are infested by goblins, bandits, mauraders, undeads, vampires, trolls, will'o'wisps, and whatever else there is ...
But the majority of players probaly don't care about that ...
On other rate I might been thinkin' there is a kind of sense in here, In the Netherlands many of the forts who where used during the sixteen/seventeen/eighteen/nineteen/ and early twenty century, are unused (but not over runned with mobs), many of them are now-a-days or just ruins, or they are museaums ... Maybe a handfull are still in use ...
Forgive me bad Ingrish I'm to lame to check my spelling