Well for one thing it makes the player who has a good skill feel justified in taking it or advancing it. Secondly it simply, in whatever way, promotes roleplaying. It takes common, humdrum rolls and uses them to create excitement or interest. You are the GM because you like springing surprises on your friends. You like to GM because you have a great world.
Good players deserve that.
Remember how the last game you played could have been better and fix it in your game. Sure it is.