Module space, module lag, dev time and resources...that, and Leanthar stated a while back that no more player housing would be added to West.
In fairness, there's nothing special about Stone. Toranites would love more housing in Fort Llast, or even Huangjin, Lucindites would like housing in Spellgard, and the list would go on. Stone was around for a long time, got destroyed and rebuilt only recently, but there's nothing truly special about it that would justify us adding housing there over some other place equally deserving. If we went that route, well, it would get out of hand.