It's an important result for post-quantum cryptography. If (when?) quantum computers are ever generally deployable, existing ZK protocols with multiple provers will need to be modified using this result. Besides, a theoretical result doesn't need immediate applicability to be important to humanity. The study of quadratic residues in Euler's time was a sort of mathematical recreation, but 300 years later it gave us the QR hardness assumption and the Goldwasser-Micali scheme and its derivatives.