Why would you think that population density would be the limiting factor when NYC, SF, and other dense urban areas in the US don't have internet access that's a

Why would you think that population density would be the limiting factor when NYC, SF, and other dense urban areas in the US don't have internet access that's as fast and cheap as is available in Japan and Europe? Note: I'm not talking about access to the vast majority of unpopulated area that is the rural US; I'm talking about the well-established high-density urban areas.