Instanced housing isn't the be-all, end-all solution that many seem to think it is. Even in an instanced housing model data still needs to be stored (i.e furniture placement etc.). Instanced rooms like the Inn don't require this as you can't move anything around.

SE's original issue with the current housing model is the server capacity needed to "add more land". More land = more server space/storage, thus instanced housing is equivalent to needing "more land" anyway because it still needs server space/data storage to be purchased; this is the part that I think people forget or don't realize.

Now, this does open up a broader spectrum for debate of SE's financials and whether or not they feel, at this point in the game, they can afford to just mass dump money into additional servers/storage for bulk housing; regardless of current ward structure or instanced structure.