Though many believe that Jesus told parables in order to make the Gospel accessible to the common people, this was actually far from the case. far from using parables to make the Kingdom of God more understandable, Christ used parables to keep "hidden," and in fact prevent people from coming to him!
Mark 4 begins with the parable of the sower, and then in verse 10 we get to the purpose of the parables.
10And(J) when he was alone, those around him with the twelve asked him about the parables. 11And he said to them,
(K) "To you has been given(L) the secret of the kingdom of God, but for(M) those outside everything is in parables,12 (N) so that
"they(O) may indeed see but not perceive,
and may indeed hear but not understand,
lest they(P) should turn and be forgiven."
The difficult part of this passage isn't as much the interpretation as much the application. There are certainly some things we ought not to do, or maybe to be more exact, ought not to claim this passage is in support of (like claiming that we ought to tell stories in sermons to better "reach" the audience because Jesus did it). But does this passage mean that we ought to make the Gospel confusing in some regards? I'm not entirely sure how this passage fits in with Paul's desire to "become all things to all people in order that he might win some." (1 Cor. 9:22)
There is however one application that I can think of coming out of this passage, and also specifically from that parable. We should not lose heart when some do not respond to the Gospel. It is Christ who hides Himself or reveals Himself to them. Let he who has ears, hear.