I respectfully disagree with this Chiramu. While many of us will and already have joined FC's, that does not mean it's a universal thing that "everyone" will do. In fact, there are large sections of the player base with no interest or desire to join a free company, and some players have no interest in joining a linkshell either. So that may be true for the majority, it's not true for everyone.
The other thing to keep in mind is that the free company house and even your personal room isn't a truly "private" space that is "yours" in game. It belongs to someone else, you still have to go through your free company house. Giving personal housing allows for a spot that is well and truly "yours".