The point of finishing the game is to finish the game. When you get to the end of the game, it's the end of the game.
Depends on one's perspective. In my case I'd consider it to be "the point of finishing the main quest is to finish the main quest", and don't think it's necessarily a good thing if the game does likewise. In some cases, with pretty much
entirely story-driven games such as the Bioshocks for example this is inevitable; but for games that are much more open, it needn't follow that the game must end once the MQ is completed and personally I prefer it when it doesn't.
