Headsets don't get pitted because of impacts or soft material. They get that way through a process called fretting (ala false brinelling). It's actually a lubricant failure rather than a material or impact cause.

Headsets are unique in that they are basically stationary bearings, subjected to lots of vibration but very little movement. The constant vibration on the stationary balls squeezes the grease or oil from the point of contact so you have unprotected metal to metal contact, which abrades the surfaces. Better riders, especially road riders spend long periods riding in straight lines, so the headset has little opportunity to re-spread the lube and slow the process.

Some greases are specially formulated for better anti-fretting properties, and help, and some designs dampen the energy, or use larger contact areas since friction is hardly a concern.

BTW- you can pull some more life out of the headset by knocking off the lower cup and crown race, and replacing them at a different orientation. There will still be some indexing, but it'll be less noticeable.

When I was in retail eons ago, this was a common issue affecting all good road bikes, and we learned that we could still ride even with really badly fretted headsets. But many people would be concerned so I started the rumor that Campy made special Cyclocross headsets that indexed this way so the front wheel wouldn't swing around when you carried the bike up embankments. That worked fine until someone walked in one day and insisted on buying a cyclocross headset.