Typically the US will build up a fleet in sz55 (with the WUS complex). Â When that fleet gets strong enough for the US player to decide to venture out, they typically want to move their fleet out but keep it within 1 seazone of sz55. Â Why? Â So that the fleet is only 1 turn away from reinforcements. Â So the fleet can move to Wake Island sea zone and still get reinforced the following turn because it is only two seazones (1 turn of movement) away from sz55.
Okinawa is 3 sea zones away from sz55, so it takes 2 turns for reinforcements to get there.
That is one reason why you might want Wake not Okinawa. Â Soloman Islands is an excellent strategic point, where if you move there in enough force you may force Japan to move their fleet from sz60 to sz61 to avoid being attacked. Â Whereas a move to Wake with the same US fleet might have been in range of additional Jap fighters from Japan that would have instigated an attack. Â Once Japan has conceded sz60 the US can waltz into EI, Car, Bor, or New and still be out of range of the Japan navy.
Those are 2 examples of good reasons why you might want the 0 IPC islands.