Your F150 is not really designed to be solely a work/tow vehicle. It's designed with a multitude of desires, ranging from a daily driver because it looks cool, to hauling mulch on the weekends, to towing a boat, to towing a trailer. Because of the variety of requirements, the manufacturer has done the best they can to accommodate everyone's desires.
If it helps, when I tow with my Ram 2500, I lock out 6th gear. No one says all gears are for all applications. Nothing to get upset about, just understand how to utilize the tool you have to it's best efficiency.
Mike