Earlier quoted context omitted.
It's the loading dock. 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; ho…
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.
Probably more effective to move the trailer wheels to the far back of the trailer.