For a game to be fun, it needs to give the player a sense that they are progressing ... getting a higher score, advancing to a higher level, seeing the next bit of the map, whatever. To play a game and score more than last time is success, even if your character ultimately fails by "dying". That reward is why we keep playing; if a game didn't give you the impression that you were getting further you'd feel like you're failing and soon give up. If you turned the score counter off in Tetris no one would play it for very long.