Matthew 13:34-35 (ESV)
All these things Jesus said to the crowds in parables; indeed, he said nothing to them without a parable.  This was to fulfill what was spoken by the prophet:
"I will open my mouth in parables;
I will utter what has been hidden since the foundation of the world."
Jesus speaks in parables, so as to fulfill prophecy. Or in doing so he does fulfill prophecy. He utters what has been hidden since the foundation of the world. Something need to be spoken of in parables, the parables work two ways. They hid and they reveal what could not be revealed in another way.
This is why preaching on parables can be a difficult thing. The Parable says it so well, It can’t be said better. Perhaps you can explain it somewhat, but the almost defy explanation, or at least many do. They speak a truth that cannot be spoken in plain ordinary speech.
This is why there are so many different genres of writing. Some genres lend themselves to revealing certain aspects of truth better than others. This is why the Bible uses so many different genres. Some things can only be spoken of in poetry, some can only be spoken of in parable, some in historical narration.
So it is even as the parable reveals truth to those who are given to understand, it speaks in such a way that the paradox of the kingdom remains a mystery. Not so much that it is “hidden” but it is still mystery.