>I'm guessing b/c it can be used to make merchandise
Weird that anyone would care, since most of those works are presumably public domain. Is it not the legal right, in most of the Western world, of the public to reproduce such works, let alone to use them as elements in their own work?
Yeah, it would probably be legal to take a picture in the museum and make merchandise, but the museum isn't going to actively help you by giving you a scan.