Why US destroyers delayed permanent helicopter facilities

Why did the US Navy omit helicopter decks and hangars from destroyer-sized ships until the Spruance class?

The Navy preferred carrier-provided aviation and avoided the cost and space penalty of duplicating that capability on escorts.

Cost and the US Navy's abundance of aviation ships, including Essex-class carriers, made permanent destroyer hangars less attractive. If a task group already received helicopters and aircraft from a specialist carrier, using escort volume for a hangar looked less urgent. That doctrine persisted strongly enough to shape even the early Arleigh Burke design without an embarked helicopter hangar. Spruance-class facilities therefore mark a broader shift toward distributing aviation capability across the escort force.