What irritates me about NCL is that they charge you a 'corkage' fee for all wine brought onboard at the embarkation port, even if you only plan to drink it in the privacy of your own cabin. Makes no sense except for another way to make more profit. Other cruise lines don't charge you any corkage fee unless you plan to drink it in the dining room. One of the reasons why we like Holland America is we can bring all the wine we want without being charged anything (unless we bring it to the dining room). I see people on a regular basis bring cases of wine onboard.
But as others have mentioned, because of the corkage fee, it's just easier to pre-order something for your cabin or buy something once you get onboard. While the prices are higher, when you add in the initial cost of your wine plus the corkage fee, it'll come out about the same amount as buying something onboard.