Collector's pay more for original finish - however much is left - because it is original. That finish is what the manufacturer put on it - and what the owner wore down using it.
If it was Jim Bowie's authenticated knife, removing the wear patterns of his hand on the hilt and blade would be destroying the history of how it was used.
If it was Audie Murphy's Garand, refinishing it would destroy the marks he put in it during the acts of his heroism.
Removing the wear patterns and markings that someone has created on that tool is, in some circles, criminal. It would be the same as buffing out the handmarks and scratches on Michaelangelo's hammer and chisels he used on his sculptures.
Patina is what tools get when used extensively by a particular human. Grandpa's old double shotgun he carried on the stage escorting gold shipments in the West wouldn't be the same all redone. You couldn't see where it lay across his lap in the dust, which hand held it, or how he used his off hand to support it. All the wear and tear would be gone. it would be shiny new all over.
And a lot of times, those who do refinish it do so in a manner about 50 years newer, which throws another discordant note into the job. A cap and ball musket from the Civil War carried by a young man who later commanded the Army, slicked out like a '60's Remington bolt action with high gloss wood, and buffed out shiny black metal? It was never done or intended to be that way.
And if the job was done 50 years ago, then changed hands, we will never know if it was the actual authentic piece used in history making moments, or some poorly done subterfuge attempting to defraud the public.
Loss of patina is the first step in the loss of provenance - and you can never go back. The first Shelby Cobra is on display at their museum - the coats of paint are chipped, revealing the various colors it was sprayed during the first year of marketing. The leather seats - ripped and horsehair stuffing exposed. The wire spoke rims still on it.
Clean that up? Nope, sorry, it would be the evidence of it's history destroyed. Destroying the patina of a collectible item is destroying history. History is what collector's pay for, not Shiny.
Most Americans have little respect for history - which is why so much of it is lost. Exactly why the original hand hammered Daytona Coupe was parked in a storage unit for decades. At least the right person got it - and he hasn't repainted it, buffed it out, or "restored" it to a finish it never had. Still has the Bonneville salt blasting on the front end from the 24 hour record run.
Of course, a new coat of paint and some glaze could fix all that up - it would look just as good as any other fiberglass kit car then.
It would be criminal.