Without question, the whole point of the genealogy in Matthew 1 was to emphasize David and how Jesus is the fulfillment of the prophecies. But that is not the case here in Luke. Luke takes the genealogy of Jesus all the way back to Adam, the Son of God.
To understand, we have to see this in context. Jesus has just been baptized and the Father says to him, “You are my Son, whom I love, with you I am well pleased.”
And then the genealogy starts, not with Joseph, but with Jesus.
The preliminary introduction is that Jesus was 30 years old when starting out in his ministry. With the genealogy, we are given his identity as that is the reason for his ministry.
From Jesus his lineage traces all the way back to Adam, the Son of God. So we have Jesus, the son of God, and Adam, the son of God which form the bookends of this genealogy.
By doing so we have the first Adam, and the last Adam. It is significant. Consider how Paul spoke of these things:
Thus it is written, “The first man Adam became a living being”; the last Adam became a life-giving spirit. But it is not the spiritual that is first but the natural, and then the spiritual. The first man was from the earth, a man of dust; the second man is from heaven. As was the man of dust, so also are those who are of the dust, and as is the man of heaven, so also are those who are of heaven. Just as we have borne the image of the man of dust, we shall also bear the image of the man of heaven (1 Cor 15:45-49).
We also see this in the book of Romans.
Therefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned— for sin indeed was in the world before the law was given, but sin is not counted where there is no law. Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come (Rom 5:12-14).
We have the first Adam who brought sin into the world. He was a son of God. Now we have another Son of God. THE Son of God. He is the last Adam. He redeems the world of sin that was put into place from the first Adam.
What Luke is doing is giving one other testimony of how Jesus is the Messiah, the fulfillment of the Scriptures. We’ve seen this a bit differently than we saw in Matthew where it is verse by verse fulfillment. Here in Luke we have testimony through the angels, through Elizabeth, through Simeon and Anna at the temple, and now through the genealogies.
And he’s not just the fulfillment of the prophecies. He is the Son of God, the Last Adam, who reverses what the first Adam set into motion. Jesus is the last Adam, paying for the sins of mankind, and sets forth a new day. One in which sin can be forgiven and overcome.