Why not plastic or fiberglass? Some plastics are crap of course but some seem to live forever. Most plastics don't get dimples--though like metal if you back into a pole they will deform and or crack--seen many plastic bumpers like that.
I'm sure they've done their research and know better than I what will work. But then they've made lemons before and only time will tell if it's the wave of the future or another flop like the unibody truck they tried back about 1962.
I'm surprised the integrated storage compartments that a couple manufacturers (I think Dodge) had built into the bed sides of their trucks haven't taken off more. Of course I don't think they did them quite right--I feel they should open more like those on service body's with door opening to the outside than tops that flipped up. I could use even some small storage space inside the bed walls but if the bed is piled deep with mulch, or a pipe rack or shell installed I might not be able to open the top of the bed rails. I think the camper specials had a compartment or two like I'm thinking. I guess the added cost and weight of those compartments kept them from becoming popular--that and that most people buying trucks are just commuting to office jobs. and have little need for places to keep straps, basic tools, chains, short shovel, jumper cables, etc.