Demand I think..
Despite their apparent popularity, rocks and mogs fits into the 1% of off-road rigs. For every rig on mogs, there's probably
2 rigs on rockwells (6x8.5)
200 rigs with 8x6.5"
400 rigs with 6x5.5
1500 rigs with 5 x 4.5 or 5 x 5.5
Plus, people do rocks mainly for one reason- It's the cheapest way to get really strong axles. Your average rockwell guy isn't looking to drop $1000+ on a set of wheels. You see plenty of people welding centers into other wheels because it's cheaper.
You also touched on another good point.. LOTS of variation in backspacing and more than that, width. Mine are a bit of an oddball, 17x9 with 6.5" BS, most run about 3.5-4.5" BS, but the whole gamut of widths, from 10-20" wide.
But there are companies making them, MRW comes to mind.
Just my observations.
