That certainly enters into it. Shitty organic pads went the way of the dodo and we have pads now that allow for better friction and cooling with less surface area. But also modern cars are cast with less steel. It wasn't uncommon a few cascades ago for the difference between nominal thickness on a brake rotor and the machine to spec to be .090.
Now days many are .030 from nominal to discard.(hell its kind of tough to even come up with a spec book it seems these days)
This isn't all bad it reduces unsprung weight and contributes to better ride and handling characteristics of modern cars.
Now we also have a problem that brake rotors now days are built of an inferior metallurgy. The engineers may spec out a specific alloy but by the time the rotors are cast in a foreign "factory" they are a hodgepodge of recycled junk with no real metallurgy.
Anyone who has ever cast their own bullets can attest to the dramatic effects alloying metals can have.
You can watch the process on youtube
I haven't seen one of those on car lathes in forever. When I started wrenching those were supposed to be taking the industry by storm. They would allow for complete elimination of runout compensating for uneven mounting surfaces and all manner of imperfections. But they never panned out around here. Mostly because we could pull a brake rotor and have it machined on the old ammco faster than we could set up the on car lathe.
In a modern shop a brake lathe is almost useless although I have turned a bunch of flywheels and machined many other things that the machine was never intended for. I even once used a brake lathe to cut wheels apart and weld back together a wider steel wheel.
