There are multiple benefits of our weekly confession of sin as part of our worship as an assembly. One advantage is that it should remind us that the time we should confess our sin is not only when we worship as an assembly.
In Psalm 51 David sang:
For I know my transgressions,
and my sin is ever before me.
Against you, you only, have I sinned
and done what is evil in your sight,
The psalm’s heading tells us that Psalm 51 was given to the choirmaster for him to set to melody and to teach to the assembly. David’s confession, inspired by the Spirit, was for public meditation and use.
What did Bathsheba think about the line “Against You, You only, have I sinned?” She would have thought David a sanctimonious hypocrite for promoting a “spiritual” pretense of repentance if it did not have horizontal implications. Imagine how grating this song would have been in Bathsheba’s ears if David hadn’t also made it right with her.
God is the lawgiver. He is the only lawgiver. We do not, and we must not, confess as sin whatever another man makes up as sin. Our corporate context reminds us that we live before God and we are accountable to Him for the revelation He’s given us. We only ever sin against one lawgiver.
But the lawgiver commands us to seek forgiveness and make things right with fellow law-breakers. That should happen whenever it’s needed; no schedule necessary.
Likewise in verse 6, when David sings, “You delight in truth in the inward being,” he wasn’t teaching us to be quiet, he’s teaching us not to cover up our sin and lie from and to our own soul.