My Dad was career LEO and instilled seatbelt use in all us kids. Friends would freak when I started the car and buckled up, as if they were about to be subjected to extraordinary “automotive activities”. So apparently seatbelt use was not a commonly practiced thing in the average household back then. Also worked in a locally owned store with a chain smoker owner, which was very common back then. I’m guessing you had a different experience growing up?