There is another aspect to this 'infraction' that has not been discussed: the visual results of accidents involving just that one time someone did not wear a seatbelt.
Unforgettable
Anyone in the traffic enforcement, emergency room, or post-mortum backroom has had their psyche shaken to the core by one of these scenes.
I know I have -- more than once (the only thing I dreaded more than a suicide was a seatbeltless victim catapulted through a windshield)
Perhaps your ticketing cop has seen his fair share.