Not to hijack the thread but.......
The picture is stored in the ship's system. The card you carry is you're boarding credential, purchase credit card and room key. When the card is swiped the picture comes up on the screen and it confirms that the card is being used by the proper person.
As to the situation in Jamaica I think it's necessary to know who is using a room or restaurant.
The days when I needed no lock on my room in Negril are gone. It's still not nearly as bad up in Spring Garden but Negril is Babylon...