What was the significance of the Messiah having to be the “seed of David”?

The central focus of the gospel is the Person of Jesus Christ God’s Son our Lord.  What about other philosophies and ideologies?  The Messiah had to be human and His humanity had to be of the “seed of David” or He didn’t qualify. David is underrated as a historical figure. Our Salvation is through the Seed of David. We miss a bit of the gospel when we don’t see the longing of the Old Testament believers for the Son of David to regain His rightful place as King of Israel.