Where I have seen them used is the truck gardens the Mennonites will plant big ones in the range of 3-4 acres of beans alone with one of these they are light so do not compact ground and you can plant and till much faster than by hand and to try that with horses or oxen would be slower and a lot more problems
are they perfect for all farming no but they fill a small special spot and there its all you need
That would appear to be cost justified for a 60 year old Allis Chalmers G, it doesn’t appear to make sense for a new tractor.