Maybe it's also how your parents prime you with the necessity. While seatbelts for cars have been mandatory since 1976 in Germany for trucks over 3.5t it's only been since 1992 and I do remember riding in a truck that didn't even have seatbelts (thus it was still ok to ride without) in the early 90s and have an uneasy feeling. Maybe my parents were adamant enough to always wear a seatbelt in the car (at the same time)... Wouldn't say I was scared, but apparently I believed them it was a good thing :P