American audiences need closure and justification. The hero has to win in the end by blowing up the bad guy - in this case, the shark. Some Asian cultures however find the death of the hero in an honorable situation quite fulfilling, but this typically loses the American audience. Just look at the box office failure of Matrix Revolutions. Consequently, the shark sequels suggest a common American concept; revenge, on the part of the shark's family - the old Hatfield and McCoy feud.