Leather is one of the most beautiful and durable natural materials. However, contact with dirt, sweat, and body oils can cause damage to the leather finish and accelerate aging of leather, leading to premature failure.
One analogy that has been used to illustrate the damage that can result from leaving the soiling on your leather, is that it is like rubbing the surface, repeatedly, with 1200 grit sandpaper. Initially it may not be noticed, but in time it will result in severe damage. Regular cleaning and protection optimize the life span of your leather and keep it looking like new.