I Love Duvets but Duvet Covers...

Duvets in general are great. Having one giant pillow covering your entire body is pretty awesome. Super warm and super comfy, you don’t even have to make your bed. But what is up with the duvet cover? Can someone not design something to hold the duvet in place. I mean honestly, it shouldn’t be too hard, but instead we buy basically a large pouch that we stuff the duvet into. With nothing holding it in place the duvet just kind of flops around, making some areas thicker where the duvet bunches up and other places bear… No good. Solutions?