There are several reasons the USMC wants to have fighters it can fly off LHD/LHAs... providing dedicated CAS for an amphib landing is only one.
In the late 1990s and early 2000s there were 3 incidents where a USN amphibious group responded to a political crisis in Africa where US and Europeans were threatened, and where there was no CVN available (due to Operation Southern Watch off Iraq, or ongoing combat ops). While the Marines were able to evacuate embassies and other "foreigners" without having to shoot their way in or out that cannot be guaranteed in the future.
The USMC wants to have strike aircraft (preferably with some A-A capability) available in case one side of the local fighting tries to block such evacuations (AH-1Zs wouldn't do well against even a short handful of jet fighters).
While the AV-8B is fine for that, they won't be around past the mid-late 2020s... the F-35B is the only option available.
In addition, the F-35B would allow the USMC to be able to forward-base fighters near a combat area without needing a very long stretch of asphalt or concrete... being able to land & take off in 1,000' or less would help greatly.
Having spent 1981-1989 in the Aviation part of the USMC, I am familiar with exactly what USMC headquarters is thinking, and have paid attention to the real-world incidents which created the perception of need that drove their specs and operational plans for F-35B.
Last edited by GreenKnight121; 18th May 2012 at 06:03.