I do think you are pointing to something valid when it comes to running a world. I also think there are different solutions to this issue (and I realize our solutions and conceptions of this may differ, but the problem is there regardless). I liken this to a divide I noticed recently among many fans when it comes to maps (and a divide I have especially seen among people who take the 'exploring the world approach'. Basically when you have a map of a province, of a region of a small area, or even a city, what does that imply about the spaces in between? For instance, I often encounter fans of Ravenloft who have a totally different notion than I do of how many towns, homesteads, villages, etc are present. Some people see the map and conclude, those are the settlements present. I look at a map and always assume this is broad stroke, like when I look at a map of the Roman empire that doesn't have all the cities (it is assumed there are places not present on the map). A GM can refine and refine, but most GMs are not going to be completely exhaustive (and this is especially true of city maps, where the street level view you describe is definitely not going to be covered unless the GM gives his city the kind of detail you would find on a modern city map or google earth). So there needs to be wiggle room here for how to manage that. The solutions I lean to tend to be utilization of a combination of randomization, extrapolation, and, very often, pinning things down as I go. But there isn't one way that works.