Why fleets still need sloops and corvettes

What role did sloops and corvettes play in fleet actions and the Battle of the Atlantic?

They mainly protected convoys and multiplied the fleet by freeing destroyers, a logic now reappearing in cheap multi-role presence ships.

Sloops and corvettes were normally convoy escorts rather than fleet-action ships, though they could release destroyers for more demanding work. Their simpler construction allowed yards that could not build destroyers to add useful hulls quickly. The Cold War expectation of rapid nuclear escalation encouraged fleets to prioritize first-rate combatants over numbers. The older escort logic has returned as modern fleets seek many affordable ships for persistent presence during a prolonged grey-zone conflict.