In Matthew 13: 10-15 Jesus is clear why He spoke in parables:" The disciples came to him and asked, “Why do you speak to the people in parables?”
He replied, “Because the knowledge of the secrets of the kingdom of heaven has been given to you, but not to them. Whoever has will be given more, and they will have an abundance. Whoever does not have, even what they have will be taken from them. This is why I speak to them in parables:
“Though seeing, they do not see;
though hearing, they do not hear or understand.
In them is fulfilled the prophecy of Isaiah:
“‘You will be ever hearing but never understanding;
you will be ever seeing but never perceiving.
For this people’s heart has become calloused;
they hardly hear with their ears,
and they have closed their eyes.
Otherwise they might see with their eyes,
hear with their ears,
understand with their hearts
and turn, and I would heal them.