Why modern navies have not standardized on 155 mm guns

Why have modern navies not adopted more 155 mm guns to share ammunition with armies?

Shipboard handling, environment, rate of fire, and mounting requirements make true ammunition and system commonality much harder than matching caliber alone.

Matching the Army's nominal 155 mm calibre does not make its ammunition a good fit for a warship. Naval barrels and firing requirements differ from land artillery, so a shore shell may use the longer gun inefficiently. A mechanised shipboard handling system can also move a larger round than crews and equipment ashore can manage. Designing one cartridge for both environments would therefore make the land system difficult to use or leave the naval system underpowered. The apparent saving in common ammunition can disappear once each service's actual weapon requirements are considered.