Q: If God already knows everything about us, what's the point of praying to ask Him something?
A: As the father of eight I can tell you that I sometimes know what my children need before they ask me. However, what I as an earthly father only sometimes know, our eternal Father always knows. No need to pull out the prayer beads or attempt to wear God down by need before you ask him!
I fear the very reason that this question is so often posed is that we have been conditioned to think that supplication is the sole sum and substance of prayer. Repeating the same prayers over and over ad nauseum, ad infinitum.
But prayer is not only a means of presenting our requests, it is a means of pursuing a relationship. It is about deepening our intimacy with Him, not just supplication. Just as I want my children to submit their requests to me as a sign of their trust and reliance on me, our Lord wants us to approach Him in prayer for reasons of relationship that go far beyond just learning the nature of our needs.