Why the Revenge class kept its three-pounders

Why were the Revenge class's three-pounder Hotchkiss guns retained?

They remained handy for signalling, deterring small craft or aircraft, and supporting troops ashore.

The Revenge class's three-pounder Hotchkiss guns were too small to matter in a capital-ship duel, but that did not make them useless. They could serve as signalling guns and harass torpedo boats or aircraft. Their small size also made them practical weapons to land with troops. Secondary equipment can survive because it performs several minor jobs rather than one decisive combat role.