They probably thought it was redundant so disabled it to avoid cluttering up the interface, but as usual couldn't be bothered to actually go through and remove the files used for it. I still recall my amusement at Windows 98 many years ago still including a version of the file manager from 3.1, even with some improvements. Strange since it had never been officially part of even 95 yet it had been upgraded to a proper 95 style program.