Safety belts were designed to keep you safe when you're in a crash. Most people know that they should wear them, but they also know that the risk of a crash is relatively low. As such, many people believe that it's not always a necessity to wear them.
Unfortunately, even if you're just taking a short joyride around your neighborhood, there is a risk of being involved in a collision. If you aren't wearing your seat belt, there is a higher risk of a few things happening, one of which is being thrown from the vehicle.