When we go to class to learn, and were are given facts, statistics, reviews, etc... We could none the less be bored to death. When a parable is told, it appeals to use emotionally. It tends to be more interesting, and when we hear or see something that requires us to remember from what was taught in the parable, it is much easier, because it is attached to pleasant memories, and the chemical mixture in our brains, aka: Emotions, get attached to those memories, thus the brain brings them back mush easier. I would tell this in a parable, but I'm a time crunch. :P
Boredom happens when learning takes a long time. Plain facts are quick so you don't get bored waiting to get to the point like with a parable. A parable is like a diamond hidden under a pile of garbage. You dig and you dig, but you get turned off, so you may never find the diamond underneath.