He worried that people would not get it - it being the message of the gospel, the Word, the announcement of the Kingdom. Jesus worried that people would miss out, be excluded from what God was doing in the advent of the Kingdom. He wanted the people to see that the new realm of God's justice was present before them in him . He wanted the scales to fall from their eyes, their spiritual blindness healed. But before they could see who and what was before their very eyes, they had to be able to hear something first.
Hearing comes first, then seeing.
When we're dealing with the Bible, hearing is believing, not seeing. For the Hebrews we hear in order to see . And so with the people gathered around him, along the sea, Jesus sits in a boat, facing toward the sloping hills just above the shore, creating an amphitheater, using the water for amplification, with the water carrying the sound of his voice. And as he sowed, some seed fell along the path,. . . . Jesus tells them a parable - the preferred teaching method in this seaside classroom.