And when they had performed all things according to the law of the Lord, they returned into Galilee, to their own city Nazareth. And the child grew, and waxed strong in spirit, filled with wisdom: and the grace of God was upon him. - Luke 2:39-40

Mary and Joseph came with purpose to the temple but, as we have seen, they took a delightful detour once they arrived at the temple.

Luke begins this narrative with the Mary and Joseph's intent to fulfill the law regarding a first born son.  You would think that this ceremony would have a large amount of detail since it concerns the Son of God in the flesh. However, Luke mentions the ceremony only in passing. He gives no details of the event itself.

I do not believe he left these details out because the law was insignificant. It was necessary that these things be fulfilled in Christ's life so that He could fulfill all the law.

Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill. - Matthew 5:17

I believe Luke mentions the ceremony this way to show that the law was fulfilled, but the meetings with Simeon and Anna were more important to the identity of Jesus.  Luke turns our focus from the law to Christ. The law points to the righteousness of God, so it is important. However, Jesus is the fulfillment of that law for us.

Our focus should be on the grace of Christ.

For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh: that the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit. - Romans 8:3-4