Transportation and other infrastructure is cheaper to build on a per capita basis. It's easier to find work and workers, especially more specialized workers. W

Transportation and other infrastructure is cheaper to build on a per capita basis. It's easier to find work and workers, especially more specialized workers. With higher density, certain services become profitable. Food delivery, more frequent and lower latency package delivery. 24 hour stores. Wider variety of restaurants. Art museums, live action theatres, sports arenas all tend to be in or near cities. A larger city also has less political squabbling because, at the end of the day, the mayor is (typically) elected at large. Look at DC and Arlington for nearby cities with arbitrary borders and the political struggles that can create. Not that big cities are immune to this sort of thing, of course, just not resistant. This is why cities tend to annex neighbors. NYC took on Queens and Brooklyn, which already had towns and a city. Regional planning was possible then. There are disadvantages though. Price, less green space, less space in general, likely higher pollution than the countryside.