One question (ok, several questions) you should be asking yourself is, "Why does God need to command lowly humans to do his bidding? Can't he do his own dirty work? If he's not omnipotent then why call him God?"
The word _need_ in that question is extraneous, and a diversion from the original question.
Given the OP postulating God existing, you presumed a need that was not a requirement in the question. For such a powerful being, need is irrelevant, compared to the objects of His orders/instructions/commands.
For your question to fit the OP, it would be more accurate to phrase it thusly:
"Why does God command lowly humans to do his bidding?"
One answer to that would be: "Because He can."
Q: "Can't he do his own dirty work?"
A: "Yes, but he can also choose to delegate it out."
Q "If he's not omnipotent then why call him God?"
A: His omnipotence is not curtailed, nor precluded, by the act of delegating certain tasks to his inferiors/subordinates/created subjects/children. You assumed a need, it was not a condition of the argument.
So, why would He undertake this telling of people to do things?
One answer would be: "To build the character of said humans."
Another: "For His own amusement."
Another: "He bloody well feels like it, what are you going to do, try and kick His butt?"
And so on.
One can always choose not to obey said God, and risk His divine displeasure. The choice, Willow, is yours.
DR