Well that's probably not too unusual given the fixed number of seats on offer & the high LF's !
Bit of a vicious circle, airport facilities incapable of A380, so would be a big jump to 773's 2x daily.
Conjecture only, but it's probably a no brainer that an A380 would have been on the cards IF NCL had the facilities to handle it ?
I am presuming that runway restrictions rule this out?, and as such nothing is going to change....