Because God for all intents and purposes is the author of the order of being. So whatever the state's official stance on God(acknowledging his existence or not) is still in the end a theological statement with profound political implications.
Without the acknolwedgement of God, the state de facto becomes the final authority and has that authority through mere arbitrary will. By contrast by acknowledging God's existence and the fact the state derives its authority from God's grace, you have the duty to hold the state accountable for any wrong doing its done - because you have a higher authority to appeal to. One major implication of this can be seen in the concept of Civil Rights for example.
So, if the state does not recognise this entity as the author of the order of being, then it's a moot point and not worth considering.