In our modern world of mass-produced commodities, stickers are the easiest way of personalizing your things. It initially spread with laptops, probably because those conferences with hundreds of people keeping identical things on their knees looked pretty ridiculous, but it works pretty well with any electronic device or really any appliance. And it's great for the children, to teach them they can shape the world around them and make it theirs, even if it's full of soulless identical things.