Parable is meant to change us, not reassure us. Parable is always a somewhat unnerving experience. I don't like it. Crossan argues that myth has as its function the creation of the belief in a possibility of permanent reconciliation between the polarities and contradictions which bedevil us. Parable hopes to create contradiction within our complacent securities.
Myth establishes world.
Parable subverts world. Parable creates humility be reminding us of limits, by enticing us right up to the very edge of certitude, forcing us to peer over into the terrifying abyss of a world we do not know. Now Jesus' primary, and certainly most distinctive mode of communication, was parable. Jesus did not talk primarily in allegory, did not preach three point sermons, did not offer little moralistic messages. He told parables.