Why did Jesus use parables to teach the people? This question was asked by His disciples in Matthew 13:10: "And the disciples came and said to Him, 'Why do You speak to them in parables?'" His answer to this question is given in Matthew 13:11-17. The first part of the answer referred to the Gentiles: "Because it has been given to you to know the mysteries of the kingdom of heaven, but to them it has not been given." The Gospel was given to the Jews first; at this time, it was not to go to the Gentiles. The Great Commission to go into the whole world had not been given yet. It was not until the conversion of Cornelius by Peter in Acts 10 that the Gentiles were juxtaposed into the kingdom. The limited Commission of Matthew 10 was still in effect and Paul said in Romans 1:16 that the Gospel had to go the Jews first. The mysteries were given to the Jews but to the Gentiles, they were not yet given.
The next part of Jesus' answer was dealing with the Jews again: "For whoever has, to him more will be given, and he will have abundance; but whoever does not have, even what he has will be taken away from him." For those Jews who chose to listen to and understand the parables, even more was given unto them because they understood what was being taught by Jesus. These Jews were already born into the house of God and had the Law and the prophets given to them previously by God, so more was going to be given to those who chose to understand. The Jews who chose not to understand, however, did not have anything and their place as the children of God was about to be taken away with the ushering in of the Christian era. So, even what they had was being taken away. As Jews, they were born into the house of God but when Christianity began, it no longer mattered that they were born Jews. Those who chose to understand would continue to obey God and continue to be children of God, being now spiritually born into their relationship with God. They would listen to the Gospel and therefore know how to continue to please God.
The Jews who are not seeking the truth are not going to find it as Matthew 6:33 says: "But seek first the kingdom of God and His righteousness, and all these things shall be added to you." God wants people who are willing to seek after the Kingdom. Jesus did not speak in parables that were impossible to understand. If a person was seeking after the truth, they would find it. In John 8:32, Jesus said, "And you shall know the truth, and the truth shall make you free." The truth was there for those who wanted to find it but for those who did not, it was hidden. "And with all unrighteous deception among those who perish, because they did not receive the love of the truth, that they might be saved" (2 Thess. 2:10). If the people had a love of the truth, then there was nothing difficult about the parables that Jesus taught. For those who had not a love of the truth, however, the understanding was just outside of their reach. This was not because Jesus did not want them to understand but because they did not want to know the truth. God does not just hand His truth over to people; He wants them to desire it and to work for it.
The Scriptures give the reason that Jesus spoke in parables: "And for this reason God will send them strong delusion, that they should believe the lie, that they all may be condemned who did not believe the truth but had pleasure in unrighteousness" (2 Thess. 2:11-12). Those Jews who heard the parables had two choices: they could believe the truth or take pleasure in unrighteousness and believe their own delusion. If they chose to believe the delusion, then the truth was hidden from them because they chose not to seek after it with a fervent love.
Finally, Jesus spoke to them in parables because it fulfilled prophecy. All of the prophecies had to be fulfilled before Christ could sacrifice His life on the cross. The Psalmist said, "Give ear, O my people, to my law; Incline your ears to the words of my mouth. I will open my mouth in a parable; I will utter dark sayings of old" (Ps. 78:1-2). This had to take place for all to be fulfilled; therefore, He had to speak in parables.