Malignant Neglect

You ask if they all have to run. No, we will always be limited by trackage, gauge and the most determinimg factor, money.
But... if you use (as G. Pitchard did) the 223 in Salt Lake City, the preservation was neither good nor benign. It was what could be defined as malignant neglect. When the wooden parts on the 223 needed preservation or even protection through a coat of paint, it was not done, there was no preservation of the exposed metal surfaces, allowing them to rust.
So... when the boys at Ogden got to it, they got a bucket full of rust and splinters. It doesn't matter that the 223 is the last Grant Locomotive, it was self destructing. Yes, you may decry the replacement of the parts on the locomotive. But who is to say that they were original Grant pieces to begin with? Remember, the D&RG rebuilt and modernized the C-16's as routine maintenance and the Grants were no exception. To leave a locomotive exposed and neglected until the parts are literally falling off of it is no tribute to the men who operated it or the railroad that contributed it or the city that displays it. It is a prime example of Malignant Neglect.
We can leave the wanton destruction by the under educated with spray paint cans or the railfan with their own "Basement Museum" to another discussion.
Do they all have to run? No, but it prevents them from becoming armor, stoves or engine blocks. Just like the last Mason Bogie in Ames, Iowa.
Rick Steele