Why Britain did not standardize on a four-inch dual-purpose gun

Why did Britain not mass-produce one four-inch dual-purpose gun and replace its other four-inch weapons?

It lacked enough anti-ship punch for destroyers, and every mount would still require an effective fire-control system.

A universal four-inch policy would leave British destroyers short of the desired anti-ship firepower. They were expected to threaten larger opponents, which favored the 4.7-inch gun in this comparison. Even a very capable dual-purpose gun on a frigate or corvette would require an effective fire-control system. Standardizing the barrel would still leave that supporting production requirement.