The Purpose of Parables

Matthew 13:10-13

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.