Say you are holding A - JYour opponent has K - Qand on the board is A - K - 4 - 7Say now that you only show your J. This forces your opponent to show you his K-Q to beat your hand. Then if you came back and showed your ace, think of how ticked off the other guy would be. By making the last call he earns the right to choose to show his cards or not.One advantage of making a call is that you get to see your opponents cards. By only showing one card, it deprives this advantage. Perhaps he was bluffing you, he would probably have mucked his cards in response to your Aces, but you could reveal his