If God knows everything, what's the point of praying?

Prayer is not supposed to give God information he doesn't already have.

Jesus actually says that the Father knows what people need before they ask—and then immediately teaches them to pray.

So within Christianity, God's knowledge and human prayer are not competitors.

One way to understand this is that knowing an event will happen is different from making its causes irrelevant. If God knows that someone will pray and that the prayer will be part of what happens next, his knowledge does not make the prayer unnecessary.

But prayer is also more than asking for outcomes. It includes gratitude, confession, lament, attention and aligning yourself with what is good.

That still leaves hard questions about unanswered prayer and God's providence. But "God already knows" is not, by itself, a reason prayer would be pointless. Information transfer was never its main purpose.