Quoted from FrostyMug:
Reason, supposedly, is the value would actually be higher if left in an "original" state.
There's some truth to this. Lets say you have a STTNG like mine where the cabinet art is damn near perfect except for :
1. some idiot that scratched that frigging Nazi symbol we all know and love into Picard's head on one side (not me)
2. some buffoon that scratched part of one side of the cabinet while moving the game into his garage hastily at 4AM when he could have simply waited until the next day to do that with a clearer mind having just driven 8 solid hours (we won't mention who that was ).
Now, the rest of the game's aesthetics are great. The playfield has some minor chipping near scoops, but nothing to get all disturbed about. Boards all match. Two plastics have some minor issues. There is a small wear spot on the translite that's not even visible.
I suppose I could get reproductions of the cabinet art, translite, and playfield and make it "perfect". That'd be stupid though. It is in rather great condition as it is! Long term, I would hurt the value of the machine if I pissed around with it from a 'serious collector' standpoint.
To contrast this, I have a Flash Gordon cabinet that is faded badly. I'll repaint/restore that. It simply looks bad, and the value of the cabinet 50 years from now wouldn't be much higher faded vs. restored.
Overall, when it comes to cabinets, I kind of consider the overall rarity of the game and the general condition of the cabinet. If it looks terrible and the game is not all that rare, it'll get restored. If I have a rare game and the cabinet looks kind of "bad", I'll leave it be (Gottlieb wedgeheads are a great example of this ... they yellow. You can scrub a lot of that yellowing away, but it won't all go away ... some of those games are highly collectible and paint job, no matter how nice, can harm the value).
Finally, if a cabinet is getting restored, I may as well consider things like clearcoats and the like since I may as well make it look awesome . On an older 80s Bally classic, I wouldn't want that ultra high shine, but on something like that Diner in the previous post, I'd *want* that look (WOW is that nice!!!! if my cabinet was considerably subpar I'd go for that look in a heartbeat!