When I was growig up, no one wore seatbelts, so, as I got older, I didn't really think that much about it. Sometimes I put it on and other times I didn't. When I got pregnant with my first son, which was before seatbelt laws, it dawned on me that it wasn't just my life anymore. I started buckling up every single time. I taught both of my sons to always buckle up ("or we're not going anywhere").
They are both grown now and they make everyone who gets in the car with them buckle up, too. My younger son had a hard time getting his fiance (now wife) to buckle up, but she has finally started doing it, too. He would refuse to put the vehicle in gear until she was buckled up. He even had me "fuss" at her. I told her that she is now my daughter and my kids wear seatbelts. I also told her that I love her and I don't want to lose her.
My mother hates them, but will wear them. My father doesn't like to wear and usually doesn't...unless he is in the car with me. He fusses, but he puts it on!