Many states have laws requiring that all occupants be belted in place while the vehicle is in motion, while some only require that those in the front seat remain belted in.
Just for safety we stay belted in, although the dogs are in harnesses, thay are not usually belted in.
If we need to move around, I pull into a rest stop or parking lot.
Me, My wonderful Wife, 2 Bluetick Hounds, a Newfie, a Cairn Terrier & a Black Lab / Newfie Mix.
2018 Jayco Alante 31v