> Everyone wants that 3,000 square foot house, and naturally it has to be within walking distance from work.
The density that was built 100+ years ago was built pre cars. The cities that are dense are dense because they happened to develop at the right time.
Now, everyone in the political process of building a new city is going to question where they are going to have space for large cars, which leads to parking lots, 35ft+ or 10m+ wide streets, and of course quarter acre lots for detached single family homes with garages and driveways.
Creating a new Manhattan type region is simply out of the question due to costs. If the nation cannot even do proper upkeep on existing Manhattan, then there is not much chance of digging all the rail tunnels and etc etc for a new Manhattan.