For the twelve years that I was living in TX I was a professional RV transporter. Of course I traveled coast to coast and Canada. Many times I used 4X4 and had one all the time. I even used it many times on wet grass, hills that were steep to get up, gravel, everything the other guys listed. Many times I had spots that I could not have gotten into or out of with out 4 X 4. This includes even my own rig.
My last truck I bout in 06, I thought, well won't need 4X4 or dully anymore, so I bought s single rear 2X2. Of course since then I have also moved to the West coast and soon back to Montana. I really regret now not having bought another 4X4. Never again will I do without. Your choice. When you need it, you need it.