A little background on why arcing happens at all and AC vs DC: https://pinside.com/pinball/forum/topic/dremmel-for-contacts#post-4235465

Suppressing arcing in a solid state game is more important because many of the electronics are easily damaged by high voltages and arcing has the potential to expose the electronics to higher voltages than they can handle. Even though the arcing usually occurs at a mechanical switch the impulse can travel through the wiring to sensitive devices on the boards unless properly handled.

Arcing on an EM game does impose some wear on the switch contacts but the contacts are usually sized appropriately to handle it. Check a pop bumper relay for example. The switch that delivers power to the pop bumper solenoid will have much larger contacts than the switch that delivers power to the 100 point relay. You'll occasionally find a resistor across a switch to reduce the arcing in an EM game but most switches are left unprotected. It probably wasn't considered enough of an issue to worry about. I'm not aware of a large scale EM switch contact wear problem so they were probably right.

/Mark