Why carriers and strategic bombers are not substitutes

What does a carrier provide that a strategic bomber force does not?

Bombers offer long-range striking power, while carriers provide a renewable nearby air base, sustained air cover, and maritime sea-control functions.

Strategic bombers can deliver a large strike at long range, but maintaining aircraft overhead from distant land bases demands extensive effort. Aircraft can refuel in flight but cannot rearm there, so sustained operations still need a usable base within the sortie cycle. A carrier can move closer, rearm aircraft, and add combat air patrols and maritime control to a task group. The point is not that one platform replaces the other, but that a balanced force may need both.