May Be a Shade Tree, but -

In my experience, the quickest way to ruin a rotor is to put it on a lathe and cut it down.

Unless rotors are heavily scored (because the pads wore completely down to the rivets - CARELESSNESS) or the rotor is warped (excessive heat - ABUSIVENESS) I would never turn them. Even then I would give serious consideration to replacing them and eating the expense as punishment for bad driving.

Being purely objective, don't brake techs have a vested interest in making the turning of rotors (at twenty bucks a pop) a routine part of pad replacement?

A consumer is at a disadvantage here; e.g., "If you say not to turn the rotors, I can't guarantee the job" or, when you give in "These are right on the margin, if I take 'em down any more they're out of spec but to save you some money, we can put 'em on and see if they hold up without warping. If they start shuddering & overheating, I'll cut you some slack on new rotors" or the ultimate "It's your vehicle but if you run through a school crossing, I ain't responsible".

If your brake tech is telling you that it is an absolute must-do even in the absence of rotor scoring or warping, I would go somewhere else or change the pads myself.

Been "done" by bad guys.

M. Allen