If you ask, "Why did Jesus teach in parables?" most people will answer: "to make it easier to understand."
When the disciples asked Jesus why He taught in parables, He answered, "
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.'
But blessed are your eyes because they see, and your ears because they hear. For I tell you the truth, many prophets and righteous men longed to see what you see but did not see it, and to hear what you hear but did not hear it. (Matt 13:13-17 ESV)
According to Jesus, He used parables not to make it easier to understand, but to make it more difficult to understand!
Why? Johnson puts forward the thought that parables were perfect for Jesus' "purposes in election".
He replied, "The knowledge of the secrets of the kingdom of heaven has been given to you, but not to them. (v.11)
I think the verse that follows contradicts the imposition of the doctrine of election into this passage, though.
Whoever has will be given more, and he will have an abundance. Whoever does not have, even what he has will be taken from him. (v.12)
I think this verse says that (even if there is no doctrine of election and we all start out with the same ability), those who have even a little bit of understanding will be given more...and those who refuse to listen to the Word will have even what they started with taken away.
But the point remains that Jesus used parables to illuminate the truth to some...and to veil it to others.