This is also true. However, the centralization causes various forms of impoverishment -- which you might also describe as "specialization." Cities develop zones around them that lack many services, but concentrate others. Think of the places where there are lots of warehouses. If you are in a city to be connected to some kind of a hub, the fact is that not all of that city's area is going to be equally well connected.

Think of what happens to towns near large cities. This has been studied by social geography since at least the 70's.