When I buy a set of tires it includes lifetime rotation and wheel balancing. Every 5,000 miles the tires are balanced and rotated and I don't have to worry about some gimmick.
If the rear wheels are out of balance it is not going to be apparent, only with the front wheels where the condition is telegraphed to the steering wheel. This is going to result in more wear on the steering components.
Cupping is the result of alignment problems or shocks that are not working properly. Rotation spreads the uneven wear though with my SUV's and trucks with IFS that problem has completely disappeared. Solid front axles put a lot more stress on the components and result in faster wear and more problems with cupping with 4WD vehicles. After switching to IFS vehicles 25 years ago I have never had a problem with tire cupping or uneven wear except if the tire inflation pressure was incorrect.