Cutting apparently duplicate ships from an air-defence or anti-submarine screen can leave a carrier group without enough coverage. A carrier group needs escorts on different bearings because threats do not arrive from a single convenient direction. Powerful sensors do not allow one destroyer or frigate to occupy several stations, conduct every task, and survive every failure at once. The extra hulls can look wasteful while they wait in peacetime, especially when their cost could fund hospitals, education, infrastructure, or debt reduction. In war, that apparent redundancy becomes the coverage and resilience for which the force was built.
Notable Point · 34:09-35:51
Why peacetime efficiency can weaken a fleet screen
A carrier group needs several escorts in different positions, so a force that seems redundant in peacetime can be the minimum needed for wartime coverage.