I think some companies running 14' trailers are hauling rolls of paper for papermills, box plants.... Some GP accounts etc.
I would imagine that it is good for hauling something like empty soda cans where the extra space is needed.
They been running them on the west coast for years. Originally, they had to banner as "oversize" which originally caught my eye, like why does that normal looking van trailer have an OD load banner ? Also, you aware a FB can be stacked to 14' high ?
They were also used for companies doing auto parts work. There were several outfits in the Great Lakes area that ran tractors that had lower suspension and frame to handle the high cube trailer. MTS and H O Wolding I think had a fair number set up like that
Costco runs 14’ dry van and reefer trailers to their Texas stores. I can’t tell that they actually load them any differently, but it does make it easier on the forklift driver with higher clearance on the roll doors.
I used to be a company driver and we did away with 14’ vans. It was a package manufacturer so lots of lightweight things. We also had 57’ long trailers. I’ve ran into a few instances where my vehicle was height checked (I run 24.5 tires and a normal 13’6 van) including the CA scale and a toll booth.