Why old sixteen-inch shells still require replacement

Did the United States need new sixteen-inch shells because it had run out of Second World War ammunition?

New shells were required because wartime stocks could only be maintained for a limited time, even if many remained unused.

Ammunition consumption and service-life management create different replacement needs. A shell remaining in inventory after the Second World War did not thereby remain usable forever. Navies must eventually replace aging stocks even when substantial wartime quantities survive. Ammunition renewal remains part of the continuing cost of a battleship-caliber weapon system.