I would bet that 99% of the pickup truck driving population has very little need for 4WD. Certainly some folks do but most don't. And the added weight and expense is a negative.
I'd say 99% of the people driving pickup trucks don't even need a TRUCK, let alone 4WD.
I see many, many trucks on the road and very, very few being used as a truck. They're as much a status thing as anything. They come with so many plush, posh options that they are more comfy than an older Cadillac. I really don't see hoe people can afford them, especially when all they do with them is drive to and from work in it.
I personally don't need a truck and I haul firewood, logs, lumber, rocks, hay, straw, building materials, scrap, etc. I can drive my little Cherokee station wagon anywhere I need to all week, but then back it up to a trailer and suddenly have a 1-ton truck. My Cherokees are about like @CWLONGSHOT 's vehicles though and for the same reason.
Trouble is - I do not see an even remotely attractive alternative in anything newer.