There are over 60 different parables recorded in the Gospels that Jesus told to the disciples and to the crowds that gathered to hear him teach and to see him heal. The Gospel of Mark doesn't usually go into great detail about Jesus' actual word-for-word teaching. So this parable about a sower is rare in this gospel and conveys its importance. Jesus is trying to telling the disciples and the crowd that faith is dynamic not static. It is about hearing, then receiving the Word of God which then bears fruit. The Word of God, spread on all different kinds of ground, is not wasteful, but produces disciples.