> And that's the problem, when the city isn't allowed to grow. The existing city already has tall buildings, so if there is more demand than supply, to create more of it you need to add more somewhere else, i.e. build some taller buildings where there are currently suburbs. Which is the thing that's banned.

The existing "city" was the suburb of the past:

* https://en.wikipedia.org/wiki/Streetcar_suburb

* https://www.youtube.com/watch?v=MWsGBRdK2N0

And as you say, the current suburb isn't allowed to change because of zoning and NIMBY. Even the current city hasn't been allowed to change and grow in many places (e.g., Toronto)

* https://en.wikipedia.org/wiki/Missing_middle_housing

* https://99percentinvisible.org/episode/491-the-missing-middl...