A cuff key in your bag will probabaly not do you any good, lets face it if some one puts cuffs on you good or bad they are not gonna let you near a bag that has survival goodies in it. If you do carry one (some states and cities look down on this) I suggest hidden some where on yourself that you can reach from the front or back. As far as why carry one, same as why you carry a survival kit to the office with you JUST IN CASE, OR WHAT IF.