Since threatening pocket books with heavy laws and fines doesn't work to coerce people, maybe threatening their intelligence will. If you are loved or if you have loved ones, you should buckle up. It isn't a matter of convenience. When someone sits in your vehicle, insist that the persons riding with you buckle up. And when you ride with others, politely ask them to do the same.
Saving lives is what seatbelts are all about.
To me, it is simple, put on your seatbelt for the same reason you don't smoke crack-because you are smart.