A friend of my father in law (I know, prime DHOTY territory, but it's true) worked as a probation officer in a youth offending unit and there were kids in there who had never been shown how to brush their teeth. Obviously that's an extreme example, but plenty of people don't know how to cook, and I'd argue that's the case more today than say 50 years ago (although I guess the overall balance might the same as I bet more men cook now than back then).