but there's no harm in asking is there?
I'm not always sure myself why we pray for things like 'peace in the middle east' or for those who are destitute except as a way of participating in God's own purposes which are always good (always always!). But, as chick-chick says its often up to us to put the prayer into action and God will inspire us to do that.
I have often found that when I pray for good things to happen it's not so much that they happen but that I am inspired to help them to happen. Our prayer affects our own response to things.
We are part of God's plan and we are His hands.