Although it is unwise to try and make every point of a parable mean something, it is still useful to dissect it a little. Notice the various aspects of the parable - the sower, the seed, and the soil. The outcome does not depend on the sower, or the outcome would always be the same. The outcome is different in the four cases only because the soil is different. The Hard Heart.
Some people listen to too many preachers.
Some people listen to one preacher too long. The problem is indifference to the message. They think that it is irrelevant to life and that they can get on well enough without it. Sometimes we need to break up the soil. The person we were visiting was the father of a member of my friend's congregation.