Wow, 40 replies! A lot of things to say about this.
I did not worry to much about being buckled when I was not in the front two seats. Never got into a accident, so I guess I was OK.
I guess if I where driving in snow or heavy rain, I would require all to be buckled.
Some have said they want to use a crock pot to cook while driving. The risk is hot food splattering on everyone inside if there is a sudden stop. I would not do it. I would not use the stove or oven while driving, the risk if something happens is to great.
Yet I will run the refrigerator on gas while driving, and normally I remember to shut it off while buying fuel!
My fuel filler is about 15 feet from the refrigerator. I have seen some motorhomes with dual fillers on the drivers side, and the refrigerator between them! Also the water heater next to that.
A big rig has to have 1/2" thick steel frame to keep the frame from twisting due to the 1400 pound engine mounted on it, that has 500 HP to twist the frame if it was not so strong! Most class A motorhomes do not need such a strong frame, and are subject to falling apart when they hit things. The box part will fall to pieces! They do not do great during a rollover event, but much better than RV's of the 70's. At least most now have a steel frame with walls that are somewhat strong.
Good luck, and have fun camping!
Fred.