Yoshida stated during the EW announcement stream iirc, that having all characters sharing one house is in the works but was also filled with excuses on why they cannot just do it just yet.

Not being able to share a house is just one of the things that we lost in their race to get housing out as fast as possible. Wait til you hear about the towers and turrets and expanded interiors that were planned as the primary use for free and grand company points but never implemented because they rushed the entire housing thing.