Why do we investigate the provenance of artworks?

Provenance research evolved as a discipline following the Washington Conference on Holocaust-Era Assets (1998) and the eleven Washington Principles that emerged from it. Among other things, it was agreed that works of art that had been confiscated by the Nazis and not subsequently returned to their owners should be tracked down. Should the pre-war owner of such an artwork confiscated by the Nazis, or their heirs, be successfully traced, immediate steps should be taken to find a just and fair outcome.