Tomay-to, Tomah-to?

I thought it was just a lazy college student phenomenon, but apparently the use of a duvet without sheets is some sort of European and British cultural oddity. I will go on record as thinking this is gross and probably energy-inefficient. The duvet is the big gun of bedding; how could you possibly sleep with only a heavy duvet year-round? Mine slowly creeps up as winter sets in; right now it keeps my feet warm, but by January I'm sure it will be pulled up to my chin. And I'll have sheets!