Was it to keep the Germans' Army Group H pinned down in Holland and incapable of reinforcing the Siegfried/Rhine defenses, combined with "We've got the Germans on the run now, let's hurry and finish them off"?
Holland was a dead end, easily defended with a minimum of forces because of the many water obstacles. Ike was ordered to conduct operations directed at the heart of Germany and the destruction of her armed forces. Or something like that. He was remarkably consistent in pursuing that strategy.