Housing is something that isn't necessary to the core of the game and is a specialty option for players to do. So housing may not be the priority, we probably assume that is why Ishgard and Idyllshire (great places to have housing IMO) doesn't have housing. Point being that housing is in a pickle as there is a high demand and not enough supply and the cost to increase the supply might not be worth it financially, really only a possibility and not a certainty.