One of the biggest deterrents to housing is that there is no communal space to entice players to stay there instead of in a town.

Some neighborhoods are also healthier than others, although that has more to do with the player community wanting a place of their own and putting in the effort to build that socialization.
For example, my FC maintains a fairly friendly relationship with our neighboring FCs and our crafters were often chatting with each other next to the marketboard. That's changed a little thanks in part to the airship workshop and forcing everyone in to an instanced room now, but it is an argument against instancing.

Instead, I'd really like to see giving people with a house the chance to really enhance the public works in their neighborhoods. Let them invite NPCs from Rowena trading company to sell tomestone gear and crafting mats to the public. Maybe a customized park players can add. Of course, there's no profit from this, but it lets players turn the residential areas in to a customized community instead of a showcase.