I don't. Derelict forts make sense in a province that didn't have a war for ages.
You′re kidding me, right?
It makes nada sense to let the area outside the city (especially the roads) fall into decay, madness and complete chaos in peacetime OR wartime. How the hell does that make any [censored] sense to you?
Maybe the army has became smaller, the equipment less up-to-date, the training and discipline less harsh... But abandoning everything in the province except the cities because no war has been sighted for some time? [censored] that.
In Cyrodiil this could be excused with the simple explanation that the Empire is crumbling, and have been crumbling ever since Morrowind. But in Skyrim there are independant Kingdoms (even more independant now with the fall of the Septim Empire) that fight and fear eachother. They cant let their defences crumble, they have to be ever vigilant against their neighbours.
EDIT: Thanks for the poll.