The big deal to the cruise line is loss profit. Think how much a mixed drink cost to make compared to how much they charge. That adds up really quick with 2000 people onboard.
Now I am not defending the cruise line. I have always brought my own rum onboard because I am to cheap to pay the liqour bill.
Celebrity Mercury - Hawaii
Princess Golden - Meaxican Riviera Oct/Nov '07
Norwegian Star - Mexican Riviera Oct '06
Carnival Ecstasy - Catalina/Mexico April '02
Disney Wonder - 3 day Bahamas Nov '99