In the middle of chapter 7, Luke makes a comment about how "the Pharisees and experts in the law rejected God's purpose for themselves" (Luke 7:30). Isn't that startling? A hammer's purpose is to drive in or pull out nail, right? But a hammer cannot prevent itself from being used to pound nails into 2x4's. A hammer cannot reject its purpose. On the other-hand, we as humans can. We can live counter to how we were intended to live, and the religious elite in Jesus' day did exactly that.
Luke 7:30 also states that their purpose rejection was related to not-being baptized by John. John's baptism was one of repentance, making an about-face in one's life. Repentance is a correction to the course of living out God's purpose. We all can get off track from God's purpose, and need to make adjustments (or overhauls). If we are consistently un-willing to make these changes though, our actions demonstrate that we reject God's purpose.