The loop is handy for when you carry your plane back to the pit area after the engine quits and you landed out there a ways. When the plane is inverted the fuel can dribble out on you. Also when nose down too. Then as mentioned it helps keep fuel from dribbling out in some of the aerobatic maneuvers too. Of course if you have a really big plane trying to carry it back nose down or inverted might not be a problem then.