Why nuclear submarines do not imply nuclear carriers

How much carries over between nuclear ship and submarine plants, older marine steam systems, and railway steam?

There is continuity in steam engineering, but submarine and carrier reactors require different plants, crews, and operating arrangements.

Naval nuclear propulsion is not a plug-and-play technology. Surface ships and submarines use power differently and accept different maintenance arrangements, so their reactor plants and crews cannot simply be exchanged. The United States Navy can draw on a larger, heavily cross-trained pool of nuclear personnel.