And when they pick up groceries they load everything onto the floor of the back seat because the bed is so high up you’d need a step ladder to use it
Another reason is to avoid letting the inside of the bed get scratched. I lived in Texas for a while, and people were that fussy about their trucks.
So true! My Ram 1500 was purchased to pull our travel trailer. It has the tow package and is factory raised up some. I'm kind of old, so I keep a three-step ladder in the bed so I can easily climb into it.
Because of the poor gas mileage, I always wonder at why people drive these gas guzzlers as their main transport. But each to his own. (BTW, some claim safety, but it's probably fashion.)
I think the more important reasons are to prevent the groceries from sliding around in the bed and to protect them from the sun and precipitation.