My biggest concern would be the greater likelyhood of mice or other vermin getting into the engine compartment, wiring harness, or inside the coach and creating havoc. This can happen even when the RV is parked on concrete of course, but I'd guess that it's much more likely if you are on grass or dirt.
Those buggers can chew through some expensive stuff. Mouse nests in odd locations can also create problems. I found a massive one in the air filter box on my pickup many years ago. Recently I had to repair all four wires to the right taillight unit on that same truck. (Brake, Tail, Backup, Ground) I need to get that poor truck into a garage and out of the barn.
2012 New Horizons 36' Travel Trailer, Front Kitchen
2008 Dodge Ram, 6.7 liter Cummins Diesel, 4WD, Quad Cab