Why is it that if we are unsure whether God exists or not we tend to think we don’t need to worship him? If an agnostic joins AA and finds that he stops drinking when he says the Lord’s prayer and turns his life every day over to God, and yet for all that still can’t rationally decide whether God exists, is he acting well or not? If you want a more philosophical way of posing the problme, there’s always Kant, who insists on the connection between speculative agnosticism and practical theism – even a very robust theism that involves providence, heavenly rewards, etc..
Hopefully, we don’t try to defend our link between agnosticism and practical atheism on the flimsy premise that the positive claim has the burden of proof. Even if arguments came with proof burdens a priori (they don’t), the claim that the positive one always has the proof burden would allow us to shoot bullets into a place so long as we didn’t know if there were any persons inside.