Why did Jesus give the disciples the secrets about the kingdom directly but others through parables?

A disciple asked Jesus why he used parables and in response he told him. >He replied, "The knowledge of the mysteries of the kingdom of God has been given to you, but to others I speak in parables, so that, 'though seeing, they may not see; though hearing, they may not understand. Luke 8:10 Why reveal it to the disciples directly but reveal it in parables to others?