It's an ideal announcement for such a situation, but to make it requires you to look in, select the PA button, make the announcement then reselect the VHF radio. Takes about 5 seconds, and given that they had possibly gone from being in the groove with 40 seconds to landing to having no power and sinking fast I doubt they had 5 seconds to spare. We used to say "aviate, navigate, communicate" and in this instance keeping the aircraft in the air then finding somewhere soft-ish to put it down took certainly took priority over talking to people. Sometimes there just isn't time to talk to anyone outside the flight deck.