Have you ever really thought about that? There may be several answers to this question and I will attempt to begin to address one in particular right now.
Matthew, Mark, Luke and John are, what I call, the bridge books, crossing from the Old Covenant into the New. Since the New Testament opens with them, we need to point out that in the context of each, they bring to a close the Old Covenant and the law and are the launching pad of the New with the death, burial and resurrection of the Lord Jesus Christ. Instead, we have looked at these 4 books as the beginning of the new without fully recognizing the importance of Jesus' life on the earth to come as a man, fulfill the law, by paying and satisfying the debt and then rising in newness of life.
Because we have not clearly seen this, we have been very confuse from time to time. We couldn't understand why Jesus said what He said when He said it. Much of the time He was addressing Pharisees and religious minded people and we thought He was talking to us. We have embraced statements, the red letter words of Jesus, m like - you brood of vipers or den of thieves. John 3:16-17 (KJV)