Other commenters replied to you pointing out the difficulty of packing things in non-grid based space, but they are only a manifestations of the fundamental rea

Other commenters replied to you pointing out the difficulty of packing things in non-grid based space, but they are only a manifestations of the fundamental reason, which is cost: it is much cheaper to build straight walls, and the furniture for straight walls can be mass made, which also makes it much cheaper. Furniture for non-straight spaces usually needs to be custom made.