A few points:
1) WWII era, low-scale maps are hard to come by, especially if one is not willing to spend serious cash.
2) Unfortunately, CM has nothing in the way of terrain types between unpaved roads and open ground. So many designers use upaved roads to represent, say, cart trails.
3) What maps I do have (thanks to the US Library of Congress captured docs collections) indicate that there was a fair amount of habitiation in Russia. Especially where fighting was taking place.
4) Fighting tended to revolve around highways and rail lines, which tended to have more population. Battles are begat by logistics, and if you cannot feed and arm your men there is little point in fighting over isolated hamlets and large tracts of forest.
So, I dont think the problem is as pronounced as you indicate. Main issue is that the quality of roads is a bit too high due to engine limitations.
WWB