It's because it's a tile based game, you can't draw too much detail in a 3x3 tile world when your textures are 16x16 px.
Perhaps that's just a consequence of the tile-based nature, but I think the spaciousness really adds a lot thematically. It's such an empty room, which highlights Madotsuki's isolation.
I like to think it's because it's actually the living room.
i just assumed Kikiyama is a terrible designer.
considering her room is p much her entire room, im glad its big lol