Horse hockey. A shop should be able to machine them flat if they aren’t approaching their minimum thickness. They are just selling stuff unnecessarily.
I do, however, replace my rotors when I do my own brake job because they are cheap and it’s less hassle than taking them somewhere to have machined. But I was able to get pads and rotors for ~120-130 on my last car. Not sure the price of JK rotors as I am new to the Jeep world.