It's time for flight decks to be fitted with a portable oxygen cylinder and mask.
Oxygen cylinders have ruptured in the past and punctured the fuselage.
Imagine the one and only oxygen cylinder for both pilots ruptured and punctured the fuselage.
Imagine cruising at high altitude, explosive decompression, (possibly taking out some avionics) grabbing for your mask and seeing the webbing not inflate.
It's a nasty scenario and one that would see cabin occupants being awake longer than flight deck crew.