I agree. Most all of the lines serve crab legs onboard at at least one meal. If NCL doesn't its because they have lessened the product so much due to cheap pricing.
All said, the best crab is not King, however. Dungeness crab is far better and is generally available fresh at several eateries at typical Alaska Ports of Call like Juneau, etc. Once you try fresh dungeness crab, you'll not care so much for Alaska king crab legs.
The only thing that comes close in my humble opinion is stone crab claws from sunny Florida.