Think about it, all those things that get on your skin during the course of a day: make-up, grime, pollution, etc. And yet many people don’t wash these from their skin before putting their face to their pillow. It’s staggering just how many people don’t wash their face before sleep.
You brush your teeth before bed, do so with your skin too.
Cleansing the skin helps remove dead skin cells, which in turn will make your skin look more radiant.