That was only 2 sides … If it wasn’t normally full of shelves and stuff… But no, thats just to have structure everywhere needed to mount door and drywall. Thats why there are 2x4s so close in remaining walls also. Nailers for the drywall..
I do have laundry or bathroom downstairs. Both small block rooms. They do each have a window though. Bad if something breaks it, but good for an escape hatch if needed.