In older houses, made from brick and concrete, that can be tricky to do. The only reason I can have my computer on a separate circuit is because we could repurpose the old three phase wiring for a sauna we ripped out. If that had not been the case, getting the wires to the fuse board would have been tricky at best.

New homes are probably worse than old homes through. The wires a just chucked in the space been the outer and inner walls, there's basically no chance of replacing them of pulling new ones. Old houses at least frequently have piping in which the wires run.