That's so it can do the endgame save. You have to hit the turn button after you meet victory conditions. That way, you can reload the endgame save and view the results and/or post the game to Metaverse. One thing you can do to avoid all that spacebar business is to put all ships in some mode like guard or sentry. That way turns don't have modeless ships to wait on. Quickest way to do that is to hit the Find button and press G on all the ships it points to.