It's harder to cut up a dense and mixed use neighborhood because the real estate is worth more and there will be more people and money to vote against it.
Boston tried that. They were able to get the project rolling in the poorer parts of town but when they got to the slightly richer ones moneyed interests rallied the Karens and killed it (racism deserves a little credit too, rich white people hate it when you build a highway between them and poor dark people). That was half a century ago. Eventually they salvaged what they could and put a light rail line in the parts of the project that had already been done but still....
The problem is that people won't let them densify without the underlying infrastructure but won't speculatively build infrastructure and won't build it after the fact. We've reached an impasse.
Boston tried that. They were able to get the project rolling in the poorer parts of town but when they got to the slightly richer ones moneyed interests rallied the Karens and killed it (racism deserves a little credit too, rich white people hate it when you build a highway between them and poor dark people). That was half a century ago. Eventually they salvaged what they could and put a light rail line in the parts of the project that had already been done but still....