As atheists, we intentionally demand evidence to provoke a sense of rationality in the minds of people with religious dogmatism, in a way to shut them up, whereas we're also greatly aware that no such evidence can be provided. These people desperately want to validate the truth of their beliefs and the annoying part is they do this by unnecessarily filling the gaps of understanding in science by a mysterious entity and its so-miracles. The most elegant and well-known method that they could come up with.
Even in the absence of knowledge, they are greatly confident and deluded in their idea of God that they have the divine arrogance to challenge an actually knowledgeable individual; and so by questioning and demanding evidence, we are simply helping them cultivate a sense of humility while also make them realise that they are as clueless as we are when it comes to proving the existence of God. It's more of a tactic than a serious request.
Theists will claim various sorts of characteristics about God's true nature, as if they've encountered or observed God themselves which thus gives them the right to make assumptions about God's nature. Let's assume a being like God does exist, how are you so sure that God is non-physical in nature? On what concrete basis did you come to that understanding? Did God have a personal chat with you and told you that?