Because nobody wants to live there. Americans by and large come in two types: the urbanists who want to live in a big city, and everyone else who wants a cottage in the woods that's file miles from a McDonald's. Sanphillippo wants a return to this 1940s idea of dense small towns, walkable towns with a population of ten thousand. He doesn't get that those towns weren't that way because everyone liked it; they were like that because they had to be. People were too poor to have a personal vehicle. Everybody either farmed and only came into town when they had to, or worked in the same factory, or worked in a store where the factory workers spent their money. Then when the industry changed the factory closed and the town died almost overnight.