Since they need a service truck to change the tire anyway the mechanic can mount the tire to the rim. Saves the cost of an extra rim I Guess. The Only reason they bother to carry spare tires in the first place is so they don’t get overcharged on the tires the roadside assistance has in stock.
Carrying an unmounted spare tire is a good idea for a long haul trucker. The tires are expensive to begin with, and even moreso out on the big road away from home. Tire shops and road service trucks know you need the tire to keep rolling, so the price is inflated even more.
I knew a guy that became a long haul trucker. He told me when he lost a tire on the road, the company would pay for it, but they wanted the old carcass back so they knew he was not stroking them for money he did not deserve.
He said his first trip he lost 4 tires, and had the old ones tied to the back of his cab.
Trucker’s wife here. We call them road gators.
I will ask him what he thinks next time I talk to him, but in the past everything he’s said sounds a lot like Zambini. He was also an o/o leased to a company (but is now a company driver). Jeez, you’re not my husband are you? 
Well said. At what point will we in this country come to the realization that cheapest (in this case inadequately maintained trucks and tires) is NOT always the best. It might just be worth it to pay $.10 more per head of Romaine so we don’t have so many trucks breaking down on the roads.
Why not charge a tax on the cost of every recap sold? This would go to pay for a tread retrieval service that would patrol the highways and pick up shredded tires.
I know if a truck in front of you drops something off it’s load and it damages your car (be it rocks, tools, branches, whatever) you’re in the right to sue them for damages. I would think retreads flying off a semi would qualify for the same thing.