I think everyone here agrees that when two pieces of metal rub together, some metal comes off. We all get all worked up on what kind of grease to put on the hinge to prevent wear, but a sear is loaded to a much higher specific pressure and is not lubricated as well as a hinge. Granted the parts are generally harder, but that doesn't eliminate wear, just reduces it.

So why is anyone surprised that a sear gets rounded after many thousands of rounds? It's just another wear part.