If you want to look at it from a conspiracy perspective it allows humanity to slow down global warming slightly while corporations and wealthy people can still pump out as much carbon as they can afford and require.
But from experience, living in a 15 minute city IS nice IF the infrastructure is good and crime is low. Still a good part of the workforce will need to commute outside of this 15 minute area, which needs further investment into rails and roads to bring blue collar workers quickly to factories and warehouses.