A lot of people probably didn't finish every quest before killing the final boss. Though I suppose it's as simple as reloading a save before starting the battle (not sure, I haven't even made it halfway through the game yet) there's no reason any longer to end a game after a final battle. Games long ago allowed you to keep going through the game world after its finished and explore some more. I think it's clearly a better choice as opposed to forceably ending the game from any perspective.
