because the audience would be familiar with them as parables were highly popular then. Also, it being a monk, it is supposed to be a serious story that teaches you something, not a funny or obscene story such as those from the Wife of Bath or the Miller.
This is also known as the "We Shall Fight on the Beaches" speech that Churchill gave during the Battle of France (which of course, the French would lose to the Nazis, who marched into Paris on June 14, 1940). Churchill was attempting to rally support from the British politicians and the people, since England too was at war with Germany. Great Britain was, in fact, on its own, since the United States would not enter the war until Japan attacked Pearl Harbor a year later.
