What does that have to do with it? Whether or not there have been instances is wholly irrelevant. The only point of no luggage on evacuation and down the chutes is to preserve life, to give those people on board every possibility to evacuate quickly and safely. Time is of the essence in an aircraft evacuation, anything that could potentially slow down the evacuation of the aircraft unnecessarily is not on ... no matter how precious you believe your personal possessions are. Life is sacrosanct and that sort of selfish behaviour is unacceptable.