Canada, they allow 2 semi trailers hooked together, a “B-train”, B trains make much more sense, unlike A trains and your picture, they can be backed up easily (with a skilled operator) around a corner. I could manage backing up both those conveyances in your picture, but the bottom one would come fairly easy, the top one would take a fair bit of practise.
Where I am, they are often used to move farm equipmnt, but not on a trailer. They strap 2, 2000 lb concrete blocks to the frame over the axle, for traction, and then use them for moving pin hitch farm equipment. “A trains” are also not “semi” trailers, least the back one, and the triple trailers you see UPS and hay farmers use in the west half are full trailers.
“Semi trailer” actually refers to the trailer itself, not the tractor. a “full trailer” has it’s own steer axle, think like a hay wagon. a “semi trailer” has it’s steer axle provided by the tractor pulling it. a “cart trailer” is like 2 wheeled buggies put half the weight on the propulsion device, often a horse. Anyways, when people say “semi truck”, they either don’t know or are referring to the fact of what it pulls, not itself…use it to pull anything else and it is no longer a “semi tractor”
Not really the poinnt bud, was talking bout the hitch