Those are fleet trucks. They are available to anyone, not just fleets. Fleet truck buyers have stopped buying manuals as well.
Ford offered the Super Duty in manual, even in the fleet configuration through MY2010. Take rate for manuals, including special orders, was at or under 1.5% from MY07 to MY10. They gave up after MY10 for the US. Mexico, the land of the no frills pickup, soon followed suit because they also had similar declining take rates.
The dealers order the trucks. Not the public. What the dealers want and what the public wants aren’t always the same. If more manuals were offered more would be sold. If they ordered 20% manuals they would have all been sold. They are cramming auto trannys down the public gullet because a take or leave it attitude is easier for them to deal with.