You can also, often, offer better odds on the US fleet as well if Japan is reliant on the carriers to land air. Since in those situations, the odds actually depend on Japan sinking the carriers and hence crashing the planes that could otherwise have a landing zone.
I want Japan to attack my fleet. If the IJN wants to leave the safety of a port and get closer to the my US bombers, please bring it. I also probably have some subs in range for the counter attack. Plus ANZAC is around to clean up any leftovers.