How do you fit a 40ft ladder inside a van? How about a mound of mulch or compost? How about hauling away customer's old plumbing or any number of filthy things you don't want in a car interior? Not to mention that when it contains heavy items like a large beam of wood, you often can't physically lift it out with those awkward van angles, but could in a truck bed.

First of all I'm not convinced that the utility of the trucks is mostly unused. This seems like a trope from anticar people. But second of all and more concretely, I've done a lot of trade work that would have simply not worked in a van, so seeing your common sentiment is always bemusing.