The problem is an economy that concentrates employment in a handful of cities, which therefore become bigger and bigger, and have the choice of building tinier and higher and denser, or farther and farther out.

Who really wants to live in the kind of megapolis that exists in Asia for example?

Europe is still livable because the countries are smaller, and they all have many pleasant, livable mid-size cities and small villages as well, not everyone is trying to cram themselves into a single large metropolis.