"save" translates into multiple languages and is recognizable by people who have never seen a 3.5" floppy disk or who are coming to computers for the first time.
Even further than that, the "Document" icon that looks like a page is becoming more and more foreign, as programs shift toward single purpose apps that handle all of their own data. It makes sense to people who are used to the paradigm of "paper" documents living in "folders" in their computer, but if you've never seen a directory or your app doesn't expose individual data files, a whole lot of other traditional icons start to turn meaningless.
If anything, I think I make an argument against it. You can make an app look like a physical address book, but I've never seen anyone use a physical address book. You could make a YouTube player that looks like a television too, but to what end? Pretty soon, people won't have seen televisions that look like anything more than a screen with a thin black bezel.
And as we move toward more unified gadgets that a lot of people have grown up with, what do we do? Make a mail client that looks like a smartphone because that's how people read mail? An eReader app that looks like a physical Kindle?
I don't think a leather address book is any more valid than a 3.5" floppy save icon. A single purpose app for contact management should reflect that it's a database of contacts, sure. Should it reflect that it's a book? Eh.
Even further than that, the "Document" icon that looks like a page is becoming more and more foreign, as programs shift toward single purpose apps that handle all of their own data. It makes sense to people who are used to the paradigm of "paper" documents living in "folders" in their computer, but if you've never seen a directory or your app doesn't expose individual data files, a whole lot of other traditional icons start to turn meaningless.