Of course, this deals with a specific zoom, which misses the point of a digital map: you want detail, you zoom in. "Overview map has fewer cities" is not necessarily a bad thing (as opposed to the other change: "roads, roads everywhere" just clutters the map).
To me, cities more than roads suggest the appropriate level of zoom for navigating because cities correlate to the density of the local road network. Without the cities there's no way of distinguishing between a highway passing through wilderness and one passing through `Super Walmarts = 1` sized towns.