Agree with Mcmaddy here - dealer is talking out of his a*se.
Most of the major panels (roof, bonnet and tailgate), will have protective plastic or cotton sheets on them, and the side panels don't actually contain any of the old transportation wax of years gone. Any half competent owner who takes a little care over cleaning his (or her) car, will most likely do a better job than the dealers. TBF, most of the time it's not necessarily the fault of the valet guys, but rather the limited time they are given by the dealer to prepare each vehicle.
About the only thing I would let them do (which is what I did), is remove all the transportation sheets, as that way all parties can agree on the condition of the paintwork (scratches, blemishes etc), before signing for the car (saves arguments later).