Every collector would prefer that the objects they collect are in an immaculate condition. For a map collector that usually includes the absence of folds, tears, or staining. Most collectors would like their objects to be in the same state as when they were issued. Or even better...: Folding maps are often flattened, monochrome maps are often colored in at a later date.
However, most maps have blemishes. Maps were often not intended to be collectors items, but were made to be used. So personally, I do not mind seeing the folds of a map that was issued as a folding map.
Blemishes reduce the value of a map. And therefore its price. And of course, I would have preferred a completely crisp and clean version of the 1933 first edition of Beck's iconic London Underground diagram. but with the small tear, and with the cropped edges, the example in my collection did cost me around 100 USD, whereas perfect examples can cost You up to 2000 USD. And in its frame, one hardly notices its faults...
Sometimes, I even find that poor state contributes to the historical value of a map. This 1944 map of Normandy for example. It is an issue of the ABCA Map review, a series of bulletins and maps produced to inform military personnel on the progress of World War II. This is the version issued in the week after D-Day.
It is not a beautiful map: just a plain black and white topographical map of Normandy. On the verso there is text and pictures explaining the sequence of the Normandy landings. Condition is terrible: Tears, pinholes, smudges, and some rodent-induced damage as well, causing loss of image.
For me, the beauty is in what it represents: how cartography was used to inform serviceman. Let's have a look at a small detail: some text in the lower part of the map.
"This map is not for the orderly room. It is to be displayed where the largest number of people in the unit can study it."
So, in my imagination, this map has been looked at by US military, in one of the most decisive months of World War 2. It may have motivated them, inspired them. And for me, that adds value.