Why Is It?

Cause that’s what mechanics do these days, replace parts. That’s where the money is, so why bother learning diagnostics, they have code readers for that.

Reline a brake shoe? You can do that?
Rewind an armature, how do you do that?
File points? Clean spark plugs?
Rebuild a carburetor? What’s a carburetor?
I've never rewound a motor, or generator, but I've relined plenty of brake shoes, from passenger car to heavy truck air brake on trailers. And I've turned HUNDREDS of drums and rotors, from Fiats, Vee dubs, to heavy trucks File points? Bet your aZZ I STILL have some points files, and carbs, I used to moonlight when I was at Miramar in the Navy.