Your question is valid, but there will difficulties answering it effectively.
US regulations require seat belts for all passengers in a passenger car and the federal regulation pretty much ends there.
I believe all states now require that all passengers in passenger vehicles be belted when the vehicle is in motion, but many have a "toothless" law. As many states regard an RV as other than a passenger vehicle, that leaves another opening.
Could you be cited for not having a seat belt on in some states?
Sure you could. But set the drill that if you are being stopped, before you get stopped everybody is back in seats and belted.
Our rule is simple: If you don't have real reason to be out of your seat, you will be in it and belted. If moving is required, it will be minimized. Traffic is a given, but remember the recent video of that coach blowing a front tire.
Matt