The airline seatbelt announcement made sense when I was a kid. Back then a lot of people legitimately didn't know how to use seatbelts because most people never wore them. Now seatbelt use in cars has been the law for children and adults for decades. Airlines have to keep the announcement, though, because it's written in federal regulations, which are notoriously slow to change. Several years ago one airline I was on, I think it might have been Virgin Air, poked fun at that in their recorded preflight announcement. "For the 0.001% of you who've never flown or been in a car before, you can fasten your seat belt by...."