There is a huge market for a simple low end no frills pickup that will actually be used as a pickup.
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.