I always get surprised by people carying non-secured loads in the car. I've been carying a callapsable ladder in my hatchback and due to the stereo in the boot it has to go behind me. I always make sure that when it's in the car, it's secured by a seatbelt so that if someone runs in to me, it doesn't end up through my spine.
I do the same for my dog, as much for her protection.
I'm intrigued that people think that seatbelts are an imposition on their freedom.
I've seen a doco on car crashes. not waring seatbelts caused more injury to passengers and others (by exiting the vehicle) than not. Air bags caused even fewer.
Only in heavy impacts did having a seatbelt on not make any difference becuase intenal organs crashed into eachother and ruptured.

Side impact air bags also had a dramatic effect on the reduction of injuries for such accidents.