Because region descriptions have a quality process and are distinctly different than a statue or monument meant to memorialize something. That someone paid hundreds of gold for so some new lord months/years later can edit it to something they want? I don't see any reason to approve this (if there's a glitch, contact an admin to manually fix it), and if there were an edit function, I think it should cost a pretty penny as you are essentially re-engraving the memorial statue or monument.
