While the story of King David is sensational and hugely dramatic, I think the reason it holds such a prominent place in 1) our lectionary, 2) in children's church story times, 3) in our collective conscience is because we can really resonate with it. The details of our lives are most certainly different, but the trajectory, unfortunately, is often the same. Listen again to the word of God spoken by the prophet Nathan.
"I anointed you king over Israel, and I rescued you from the hand of Saul; I gave you your master's house, and your master's wives into your bosom, and gave you the house of Israel and of Judah; and if that had been too little, I would have added as much more. Why have you despised the word of the LORD, to do what is evil in his sight?"
Do you hear it? Do you hear what I hear? It is the human story - God gives and gives and gives; God desires to give even more; but we decide we'll take it on our own; and, inevitably we do what is evil in the sight of the LORD. This is what sin is, taking on life by yourself - it leads to greed and glutton and pride and envy, but it all seems to start with a lack of trust in the promises of God. It all seems to come from a forgetfulness of God's prior faithfulness. God gives and gives; God desires to give even more; be we forget that, thus far, every promise has been fulfilled, and so, we attempt to do it on our own. We turn from the way of God and follow the path of our own devices and desires. We do what is evil in the sight of the Lord.
But there is good news for us (even if the lectionary folk don't want us to hear it.)
2 Samuel 12:13a reads - "David said to Nathan, 'I have sinned against the Lord.'"
The lesson for Sunday ends there, but 2 Samuel 12:13b reads
"Nathan said to David, 'Now the LORD has put away your sin; you shall not die.'"
As easy as it is to forget God's faithfulness and go our own way - it is that much easier to repent and return to the LORD. Confess and be forgiven.
That is the good news of David's life, the good news of our lives, the good news of all eternity.