Fridge contemplation. Really just need to go camping.

While underway, the fridge operates fine when off level due to the motion and vibration of the vehicle. A level switch would likely be turning the fridge on and off frequently in that situation, and that of course, would not be good. There are some makes/models with an "out of level" indicator though. Both Dometic and Norcold say that if the RV is level enough for comfortably moving about, the fridge is level enough.

The usual reason...cost.