You don't have to....I never had a problem getting rotors back damaged....and I know the shop I used to go to rushed on tires. I personally saw a guy throw my rear wheel on the ground....rotor side down...guess I'm glad he knew nothing would touch but rubber on that side.....but I couldn't bring the wheels back after seeing that ...not without removing rotors and sprocket.
If you bring the wheels in without rotors and sprocket, they are impossible to balance. So that is the downside....upside is that balancing a motorcycle wheel is not really necessary.
So pick your poison: Possible warped rotors from abusive shop grunts or unbalanced wheels.
I just do my own tires now.
'08 MIDNIGHT SAPPHIRE BLUE Now Deceased