I have been lurking on here for a while and decided to finally chime in.
SS series, like many have mentioned, is a sailing simulator not really focused on sinking. I think what they have is fine. Too add graphics for a splitting ship, or damage caused by rushing water would be very taxing on the current computer systems.
For those that want a sinking simulator, may I suggest the Silent Hunter series?
http://www.youtube.com/watch?v=3foDiz4ItII
http://www.youtube.com/watch?v=1wfRCMv3sNo
Honestly, ships sink in many different ways, and to add that to a game would be pretty rough. The physics involved in such an operation would be pretty substantial not to mention it wouldn't add that much to a game.
Then, like others have said, you would get companies not wanting their logo going to the bottom of the sea.
There are plenty of life videos of ships going down on YouTube as well. Even on US TV, the Discovery channel did an entire hour documentary on sinking an air craft carrier for an artificial reef. Needless to say, it took a while for her to go down. They had to set explosives off at precise time to get her to lay on her keel so it wouldn't be dangerous for divers.
The only way ships going down abnormally fast would be breaking apart, explosions, warfare, capsizing, rouge waves, etc. Unless you want to spend 30-120 minutes watching one go down, it's a waste of resources (programmer and computer) to add that into the game.