It just makes it a lot easier to keep what you have in your invetory, because if you had armor on, and you opened the casket, that would be even more stuff you lose if you die. However, if you only wore like 2 pieces of armor, and wield a weapon... You can just keep the casket and drop everything else (as McGuff said), and use protect items prayer. That way you don't lose anything at all valuable and you get to keep your 2 pieces of armor, weapon, and the casket. Remember, it is very easy to get back a spade, watch, etc...