That's a good point. It would have to be the right set of circumstances: with unused land in close proximity to an existing city that can't manage to scale up

That's a good point. It would have to be the right set of circumstances: with unused land in close proximity to an existing city that can't manage to scale up because of entrenched interests. I suspect such areas exist (perhaps around Salt Lake City, or Las Vegas) and there might be a chance to make a true dense city in those areas rather than the sprawl that has developed naturally.