What is a parable?
According to Google, a parable is:
"a simple story used to illustrate a moral or spiritual lesson, as told by Jesus in the Gospels"
Ah, that probably explains why JESUS teaches us through parables.
But let the LORD tell you Himself why He speaks to us in parables:
Matthew 13:10-17 (King James Version)
10 And the disciples came,
and said unto him,
Why speakest thou unto them in parables?
11 He answered and said unto them,
Because it is given unto you to know the mysteries of the kingdom of heaven,
but to them it is not given.
12 For whosoever hath,
to him shall be given,
and he shall have more abundance:
but whosoever hath not,
from him shall be taken away even that he hath.
13 Therefore speak I to them in parables:
because they seeing see not;
and hearing they hear not,
neither do they understand.
14 And in them is fulfilled the prophecy of Esaias,
By hearing ye shall hear,
and shall not understand;
and seeing ye shall see,
and shall not perceive:
15 For this people's heart is waxed gross,
and their ears are dull of hearing,
and their eyes they have closed;
lest at any time they should see with their eyes and hear with their ears,
and should understand with their heart,
and should be converted,
and I should heal them.
16 But blessed are your eyes, for they see: and your ears, for they hear.
17 For verily I say unto you,
That many prophets and righteous men have desired to see those things which ye see,
and have not seen them;
and to hear those things which ye hear,
and have not heard them.
Matthew 13:34-35 (KJV)
34 All these things spake Jesus unto the multitude in parables;
and without a parable spake he not unto them:
35 That it might be fulfilled which was spoken by the prophet,
I will open my mouth in parables;
I will utter things which have been kept secret from the foundation of the world.