The idea that "the future" is a megapolis that needs to be built up really needs to be defended a bit more. Historically, the dense megapolis has been the futur

The idea that "the future" is a megapolis that needs to be built up really needs to be defended a bit more. Historically, the dense megapolis has been the future, but that might have just be an accident of technology's evolution. Why can't Earth be densely covered with smallish cities like current Berkeley and San Francisco?