Fran that is the unknown delema that is a curse upon the disobedient children, in that deceivers themselves don't know they are deceived...However, Jesus gave the solution to the matter in the parable of the sower in Matthew 13:10-15. This is why he spoke to them in parables. He also said in Mark, that if one doesn't know the parable of the sower, how are they to know the other parables...Example they know not the parable of the prodigal son because they never came to grips with the parable of the sower, thus the grounds of the heart were never broken up in repentance in order to receive the engrafted word that is able to save the soul. Therefore the heart remains unplyable and cannot receive anything from the Spirit of truth.. But to those that make ready and brake up the grounds of the heart in repentance, He said; blessed are your eyes, for they see: and your ears, for they hear. The rebellious flesh cannot hear nor contemplate such spiritual matters, therefore Jesus spoke to them in parables in hopes of stirring up their fogged minds, in that they may earnestly seek with diligence the truth hence forth brake up the fallow grounds of the heart in repentance, and then hunger and thirst for righteousness so that they might be filled...
Good explanation for why Jesus used parables.
He also wanted some effort made to understand Him. Also by speaking in parables people could add their own understanding by experiences had by them instead of being told exactly what they should think.
We follow jesus with our heart, not a bunch of rules, so he wanted people to understand with their heart.
But some had hard hearts. No ears to hear...
When we dont like what is being said...we dont want to hear.