Believers are often hypocrites. You ask them why a child dies with cancer and they'll say God has a plan and works in mysterious ways. Yet they'll kneel a pray for God to heal a sick child dying from cancer to ask for something OTHER than God's plan. If it is God's will that the child dies then prayer is not trusting in his plan... it's asking him to change his plan
With your thinking though there would be no reason to pray to God for anything because He just runs on batteries.
i think where people go wrong in prayer is asking for the wrong thing or with wrong motives ect. But beleivers are called to pray in Gods will according to and in accordance to His words..