Jesus often communicated spiritual truth through parables - short stories or descriptions that take a familiar object or situation & give it a starting new twist. By linking the known with the hidden & forcing listeners to think, parables can point to spiritual truths. A parable compels listeners to discover the truth for themselves, & it conceals the truth for themselves, & it conceals the truth from those too lazy or prejudiced to look for it. In reading Jesus' parables, we must be careful not to, read too much into them.
Why would a farmer allow precious seed to land "by the way side," upon rocks, or among thorns? He is using the acceptance method of hand-seeding a large field - casting it by handfuls as he walks through the field. That some of the seed produced no crop was not the fault of the faithful farmer or the seed. The yield depended on the condition of the soil where the seed fell. It is our responsibility to spread the seed (God's message), but we should not give up when some of our efforts fail. Remember, not every seed falls on good soil.
God told Isaiah that people would hear without understanding & see without perceiving, & this is what happened to Jesus. The parable of the soil was an accurate picture of the people's reaction to the rest of his parables.
Wayside people, like many of the religious leaders, refused to believe God's message. Hard-rock people, like many in the crowds who followed Jesus, believed his message but never got around to doing anything about it. Thorn-patch people, overcome by materialism, left no room in their lives for God. Good-soil people, in contrast to all the other groups, followed no matter what the cost.
Reference summary used from the Life Application Bible KJV, Tyndale House Publishing, Inc., Wheaton, Illinois