The title is a bit of an exaggeration.
Why do corporations change shampoo and toothbrushes so often? I’ll go through 10 different shampoos and toothbrushes, then find ones I like. I’ll probably be able to purchase them again a few times before the ones I like are no longer available.
What are the forces driving manufacturer’s to change their basic wares so often? Besides Wall St. greed, that is?
Same reason software will make pointless UI changes. Keeping things fresh gives their users the “exciting” feeling of novelty without having to switch platforms.