When we had our Bounder and the DGKs were small, they were to be buckled up when seated.  And because the dinette was so da## uncomfortable, we allowed them to get up and stretch and maybe get something from the fridge, they were also allowed to lay on the beds but no potty unless we were stopped.
As they matured and so did our attitudes, it became any time the ignition was on the belts were too.  We also moved from a 27' with the captains chairs up front and a very uncomfortable dinette(the only seating outside the cab with belts) to the captains chairs, dinette(pretty comfy) and a sofa(very comfy) so being seated for longer periods of time isn't so bad.  Besides the advent of age has caused the need of exercise to relieve arthritis pain and the need for several stops after two cups of coffee in the morning, it gives everyone the chance to hit the head and stretch the muscles.
So now, while the rig is in motion the captain is the only person allowed to get up and use the potty.  Don't want to burn daylight with rest breaks and the CC works right?  It's sort of like; I don't allow anyone else to sleep while I'm driving.  
Hopefully, Humor can be a very subtle way of pointing out the importance of using common sense.