The problem comes when you change to a new CAD system and don't bother to convert all of the existing designs. Eventually there is no one left in the company who remembers where the old stuff is, assuming it still exists, and you have no way of reading it anyway. Not a big problem if you are just making throwaway toys but a serious problem if you are expected to maintain machines over a fifty year lifetime. In the past a big engineering company would have a drawing office archive and even have a librarian. Now disk space is so cheap we can store everything but we can't make use of it because file formats become obsolete in a way that drawings on paper never do.