The Parables of Jesus, contrary to popular opinion, were not given to clarify spiritual truth for everyone that heard them. They were in fact given to obscure and hide the truth from some and reveal the truth for those who had a heart which receives such truth. When Jesus explained the purpose of his parables, he said just that.
And when he was alone, those around him with the twelve asked him about the parables. And he said to them, "To you has been given the secret of the kingdom of God, but for those outside everything is in parables, so that 'they may indeed see but not perceive, and may indeed hear but not understand, lest they should turn and be forgiven.'" (Mark 4:10-12) - The sheep and the goats - The ten virgins - The talents - The wedding feast - The four soils (The sower) - The unforgiving servant - The pharisee and the tax collector - The Good Samaritan - The Prodigal Son