I would think it's possible that they haven't been scanned or reproduced in any way, so as to avoid their being obtained by anyone else. I remember talking about this before, and someone speculated that Batman's copies might be the only ones. (But that would seem odd for the GCPD to agree to that. But then again, Babs being the commissioner's daughter, it would be understandable that those involved wouldn't want just anyone in the GCPD with access to case files to be able to go and look at them, you know?)