To keep parable and their explanations together in a Sunday reading, the lectionary chops Matthew's Gospel up a little funny these weeks.
But left out entirely is the explanation of WHY Jesus uses parables:
Jesus told the crowds all these things in parables; without a parable he told them nothing. This was to fulfill what had been spoken through the prophet:
‘I will open my mouth to speak in parables;
I will proclaim what has been hidden from the foundation of the world.’
- Matthew 13.34-35
The citation from the "prophet" here is actually Psalm 78.2. Jesus teaches in parables in order to proclaim that which is hidden, and has been hidden, from the beginning of the world. The parables, by their very difficulty, hide and at the same time reveal. The hidden God is also the revealed God.
If this mystery doesn't make sens, look at your spouse or significant other sometime. how much do you really know that person. I look at my wife sometimes and wonder, "Who are you?" We remain mysteries to each other, even as God remains a mystery to us.