It's true for antiques and collectibles, too. Even in a down market, prices hold-up better for the top examples of any type of object . A good provenance hikes the value and adds to the resaleability of an object.
People love a story.
Nobody sees the signature on a Cartier brooch. For resale value, it's got to be there. Sure, you can have a piece restored, but it will never be as desirable as something that was never damaged. Over time, fewer items survive and those that have survived usually deterioriate. Your investment goes up because you take care of it.