Years ago, long before I started driving, it was common to have a motorized grinding wheel that mounted on a fixture in a manner like a drum lathe tool bit does. The reason for using the grinding wheel was that hard spots in the drum could be ground smooth without ripping out the metal like a standard steel tool bit did. When carbide tool bits became commonplace, there was less need to grind the hard spots out, and since time equals money, and real machinists get real money, grinding drums went the way of the Dodo.

Same deal with arcing brake shoes. It's hard enough finding competent machinists, and if you do, they want to be paid. Besides that, people realized that asbestos dust if harmful to your health. Eventually, more parts suppliers started stocking oversize shoes that worked well enough without needing skilled labor to make them fit the drums. .030 and .060 oversize became commonplace. When I would do stock updates, I even found shoes in parts stores that were .090 oversize. Drums would be getting awful thin at that point.