I won't quote the whole section, but I wanted to question the comment on coils being cheaper.
In addition to the cost of the actual spring, a coil suspension adds: radius or control arms, and a track bar (panhard rod). As well as attendant mounting hardware for these items.
A leaf spring has the magic of acting as both a spring and locating the axle, while a coil separates these functions.
While I am sure leaves have some specific advantages, I can't think of any right now. I have found coils easier to work with in terms of changing ride height and springs.
Perhaps it is the ability to use an overload leaf that took the 1-ton down this path.
And.... Lord I can't believe I am wading into this.... Regarding axle wrap, it's generally the same story as above. A leaf spring is locating the axle and suspending it. Although some vehicles, Wrangler, have used leafs with a track bar.
Leaf springs, especially those with any blocks, can allow axle wrap. This is what those "traction bars" on 70s muscle cars were there for. A coil spring, which is controlled from rolling front to back by radius or control arms, will control this wrap better than a plain leaf.