After surviving for twice as long as it's design life, it is a tribute to the origonal design and strength, but eventually there has got to be some reservations about it's stuctural integrity. So instead of flying civilians, where if an 'incident' were to occur, the outcry and compensation claims would be a serious black mark, just use it for military purposes where the 'compo' claims would be limited by MoD 'rules'.
Just as a matter of interest, when was the last loss of a 'Transport Command' aircraft with family/civilian passengers on board ?