Cutting the commutator is a method to extend the useful life of your motor, at the same time increasing the performance. It's a win-win situation.
The primary cause of wear of the commutator is due to arcing, which erodes the commutator. As the commuator wears, it arcs more, which causes it to wear even faster. Plus, as a commutator wears more, the contact area of the commutator changes, which decreases the time each pole is energized, which lessens the power output of the motor.
Touring cars will be harder on commutators than 1/12 scale cars, due largely to the fact that 1/12 scale cars use 4 cells, as opposed to the 6 cells used in the outdoor cars. So, commutator wear is a much larger issue with Touring cars than it is with 1/12 scale cars.
Part of that is offset by the current 1/12 scale club motor; the MVP tends to wear out the commutator much faster than other styles of motors.
People may very well cut the comms on their 1/12 scale motors more than their 1/10 scale motors, but that is due mostly to factors other than the respective wear rates of the commutators, since 1/12 scale motors tend to last so much longer than ones used in 1/10 scale cars.