Why a battle fleet still needs island bases

Why would the United States need island-hopping if its intact 1939-40 battle fleet could seek a decisive fleet and air battle?

Because the fleet still needs sustainable forward bases and additional axes of attack; forcing battle does not remove the logistics required to move and support naval power across the Pacific.

An intact battle line still needs repair, fuel, aircraft, supplies, and operating bases closer to the combat area. Capturing or using island positions creates sustainable forward locations and another direction from which to pressure Japan. The United States could seek a decisive battle while building the logistics needed to reach it. That preference would have to be reconciled with Britain's slower blockade strategy in a combined plan.