Like all of these stories it is hard (due to the dreadful standards of modern journalism) to really know the facts and until results of any enquiry are published it is a bit early to start pointing fingers at Carnival.
It may be that some punter has mentioned to a utility bar steward who speaks limited English that she has seen a boat with people waving at them, the utility bar steward has smiled and nodded and said yes ma'am and that is what the press are reporting as the cargo having informed the crew.
I am fairly sure that the captain would not have sailed past a boat which he believed to be in peril, the report that I read was that neither the officer of the watch nor the captain had been informed, the officer of the watch would have only monitored the boat in terms of a potential collision and when he or she was satisfied that there was no risk of collision then they would not have been looking at it in terms of possibly being in peril.
The cruise companies are all aware of the publicity impact of ships carrying out rescues, both in terms of the cargo onboard at the time seeing the spectacle of "survivors" being brought onboard and in terms of press coverage, so it is highly unlikely that this will have been a conscious decision made by someone at Carnival.
Unfortunately regardless of the details of this event, both piracy and the unwillingness of countries to accept survivors who may be wishing to claim asylum does make carrying out rescues at sea a decision which now has to be risk assessed rather than an automatic reaction.
