Not long ago I discovered that something I took for a fact is not always true. How do you make a bed? Fitted sheet on the bottom, then a top sheet, then a comforter/duvet on top, and an extra blanket in between the sheet and the comforter if it's cold. Right? This just in: not everyone makes their bed this way. Australians typically use the fitted sheet on the bottom and then a duvet on top- that's right! No sheet! They routinely wash the duvet cover, so it's not as gross as I originally thought, but still, how do they regulate temperature when the only choice is duvet or no duvet? The sheet has its place- namely, when it's too hot to sleep with a duvet on top of you but you don't want to be completely uncovered.
I once said to my Irish flatmate something along the lines of "isn't it weird that Australians only put duvets on their beds and not a sheet?" and she responded that that's how they do it in Ireland, and "sheets are for hotels and Americans." I still think it's weird. Who sleeps without a sheet?