I'll be shopping for a new (or new-ish) truck shortly for pulling a medium size trailer or 5th wheel. It seems like the vast majority of 3/4 and 1 ton trucks around here are 4WD, with jut a few 2WD...
In the West, 4WD is very useful. We need to be able to drive in snow and on dirt roads when not towing. I have towed a small trailer and boats in the snow, and used 4WD many times. The CHP is tough and requires chains on the rear driving wheels during snow storms even with 4WD.