quotes from Chapter 20 Does God Really Need Our Prayers? by Dutch Sheets
I highly recommend you read this chapter in its entirety at Pray! Magazine Archives.
"God's decision to do things on earth through human beings cost Him dearly. He had to become human in order to regain what Adam gave away. Nothing is weightier proof of the finality of this 'through humans' decision than the incarnation. God clearly intends for humans to be the link to His authority and activity on the earth forever. This is why prayer is necessary. God works through the prayers of His people."
"God, in His sovereignty, has chosen to limit Himself on earth to working through humans. Since it's difficult to believe that it's God's will for the earth to be in the condition it's in - or that He's powerless to do anything about it - we can only assume that He is waiting on something from us to bring about the necessary changes."