They are there to give the atmosphere of a ravaged world in a constant state of disorder and decay. In the beginning, they weren't that clearly marked. They are also there to give you a feeling of "biggness". This house WAS bigger once, but now it's a crumbling mess.
So instead of giving you heaptons of useless rooms to go to just to make the world "bigger", the destroyed rooms are marked as such simply to just show you the world is big, but you don't need to explore it. I'm not sure I'm getting my point across (post-dinner coma) but I hope you understand the point.
There is never any reason to go to those rooms. They are simply there to artificially enlarge the world and point out that "Hey this world is going through a tough time, yo".
EDIT: Atrocious spelling.