As children, didn't we all have imaginary friends whom we spoke to, shared our secrets with, introspected our decisions with, and looked on for strength against our fears? Sometimes even blamed these non-exists for all the troubles that befell.
So how different were those child phased imaginary people from the adult phased god. The purpose is essentially the same, just different semantics.
Adults never wanted to grow up to take full responsibility of their actions. We have been thrust with it. I am not denying that we adults do not like the benefits of being so but we could do away with all the musts, shoulds, have-tos, and necessities. If we could retain the benefits without shouldering the difficult stuff we would gladly trade it.
So what is god for us?
God is our crutch!
God is the magic that exists within our banal lives that gives us the reassurance to continue when all looks desolate. God gives us the hope that good times will continue and bad times shall cease. God is our driver into the unseen future. God is our 'get out of jail' card the the game of life when the dice throws in a bad number!
We depend on God because we cannot depend on life and we all need assurances to continue from this moment to the next!