The important thing here is to recognize the political reasons for why restrictions on density and creating new urban housing exist. So long as urban sprawl is

The important thing here is to recognize the political reasons for why restrictions on density and creating new urban housing exist. So long as urban sprawl is an easy possibility and the status quo solution for expensive housing is to implore young people to simply move further away, there will be little to no political pressure or incentive for politicians to upzone urban areas. Essentially new development in greenfield or brownfield areas shields established urban residential areas from needing to be redeveloped.