The vast vast majority of trucks are not filled to the brim (and even if they're at their weight limit, they often have "air" in the box).
"Lowboys" are mainly used for large construction equipment where they need the extra height.
A semi-trailer is a surprisingly cheap piece of equipment.
Some trucks that are special purpose use the lower areas (see https://www.mayflower.com for an example; household movers have more weight capacity than space).
Retrofitting loading docks to work with lower-floor vehicles would be trivial, not to mention many buildings that could not accept deliveries would be able to.
If the trucking industry didn't want to spend $127 per trailer to add underride protection, I doubt building owners will want to spend what is likely to be several thousand dollars or more on retrofitting their loading docks.
That presents problems navigating tight corners where tractor trailers already have difficulty. I see some trailers where the position of the wheels can be adjusted. I wonder if that is for weight distribution or for the roads planned to be driven.
The vast vast majority of trucks are not filled to the brim (and even if they're at their weight limit, they often have "air" in the box).
"Lowboys" are mainly used for large construction equipment where they need the extra height.
A semi-trailer is a surprisingly cheap piece of equipment.
Some trucks that are special purpose use the lower areas (see https://www.mayflower.com for an example; household movers have more weight capacity than space).