Why ask God to remain faithful as if God needed reminding

Why ask God to remain faithful, as if God needed reminding? Psalm 71:9-18

The same question might be raised about any prayer on any subject. Why articulate requests to a God we confess to be omniscient? Isn't that like telling a math wizard that two plus two equals four?

In fact, prayer often recites the virtues of God in a way that serves our own memory and faith. We may passionately ask God to care for us, knowing full well that every promise in the Bible says He will. Such a prayer constitutes a reminder to us, since we cannot imagine in any real sense that we are informing God about matters unknown to Him. That we should pray is a clear biblical mandate. Intimate communication with God is the believer's privilege. Impossible by human skill alone, each prayer is a miracle.