Back in the early 1980's in the Adirondacks, we hauled the bulk of our firewood in a 2wd '78 Ford single cab, 8 ft bed (nice metallic deep forest green). I want to say it was a Ranger back when they were a full sized truck. I couldn't stand that it was 2wd, but the farmer up the road had a Chevy he used in the fields when picking corn. I think that was 2wd as well but I'm not sure.I had a 2wd F350 work truck that got the same 12 mpgs as my 4wd F250. Both trucks had a 6.2 with a 6 speed. All the gas 3/4 ton and up trucks are thirsty. The diesel is a $12k upcharge so I doubt diesel buyers are going to squawk over "having" to spend a little bit more on 4wd.
If Ford was selling a bunch of high trimmed 2wd SD they would keep making them.
My grandpa had a farm in Kansas. He always had 2wd trucks. Every farmer in that same area now has 4wd trucks. 2wd just aren't that popular anymore.
I think 4wd started coming more into play when people wanted to branch out on their own and make some side money plowing snow, instead of using a 10-wheeler AutoCar or IH. Maybe that's when it started. 70's or 80's and picked up steam in the 90's when people like me, who resented our father's 2wd trucks ever getting stuck went out and bought 4x4's for x much more versatility and capabilities. And... that much less towing and that much more maintenance costs
Only to find out 4x4 is helpful, but 4x2 gets you 90% of the way, and some good judgement gets you farther.
Yet, I still would not want to buy a truck without 4x4, at least, not for me