Snakes are unique among wildlife for many reasons, and one of those reasons is their ability to shed their skin in its entirety. We don't see this from other animals, so why do snakes shed their skin whole?
Put simply, snakes shed their skin because it doesn't fit anymore or because it's old or worn out. When snakes grow, their skin does not, so they outgrow it. When this happens, they shed their outer layer of skin. A nifty trick to have when you don't fit in your skin anymore.