Grew up in the Midwest. Unusual in my family and circles. I’ve known what they are since some time in my teens (there’s… a chance the film Fight Club’s actually the first time I both encountered the word and put together some idea of what it specifically meant, though I’d heard it before and thought it was just a fancy word for “comforter”) but we never had any, I’ve never put a cover on one, and I’ve never seen someone putting a cover on one.