Drive shaft out of phase

Probably a combination of different materials (less dense steel?) and thinner, cost of parts (just buy a new set), and time (why turn when you have parts stores on every corner with replacements)

 

Rotors and drums are cast iron. I can say from experience that the quality of the metal used has definitely decreased over the years. And yes, they are definitely being made thinner. So with that and the cost of a new set, the turning business has practically dried up. It's almost standard practice now to just replace the rotors when doing a brake job. Cheers