I know for a fact Carnival has excellent security and a strict no tolerance policy.
It seems like the other cruise lines should be monitoring the crew a little better, honestly. You can't just leave it up to customs.
I would bet some people bring a little on for personal use, but if someone had 33 kilos hidden somewhere they would be crazy to risk getting caught by using it onboard. But then again drug smugglers are not always the brilliant people the movies make them out to be.
It does bring into question other things. Remember in "Scarface" when he is saying "I don't like Columbians" - well, some of those people can be pretty rough. In LA the Jamaicans actually had a reputation for being quite street tough - and that is who they just caught.
You have to wonder about guns and other things that may have been involved although none were reported.