Talk:Home/@comment-75.119.243.68-20120807045655/@comment-4674838-20120807050708

It's because those rooms do not meet the NPC block requirement. NPCs require an empty block to stand on that must be adjacent to a table/char (but blocks which the table/chair are *on top of* do not count) and sufficiently far enough away from the walls.

NPCs behavior at night requires them to stand on a solid (non-wood-platform) block which is adjacent to a comfort item. Basically, your room does not have enough empty space to accomodate this part of the NPC routine, so the room is unsuitable.