This language is no longer necessary for copyright. And yet, it persists.
"PSA: The phrase “All Rights Reserved” isn’t necessary today, but it does have historical origins.
In order to understand why “All Rights Reserved” isn’t legally necessary for copyright protection, it’s important to remember that the Berne Convention for the Protection of Literary and Artistic Works — which has 176 contracting parties — did away with formalities. The Berne Convention, which sets minimum standards for protections, provides automatic copyright protection — that is, copyright exists from the moment of creation and is not dependent on registration or notice. While formalities, like registration, might still be required in order to obtain certain remedies (for example, statutory damages in the United States), the existence of copyright is not dependent on such formalities. While notice is no longer required for works created today, it can still serve a useful purpose, for example, to provide information to users that the work is indeed under copyright protection and provide evidence in a copyright infringement case. “All Rights Reserved,” however, is more of an historical remnant."