I'm not going to defend Mormon beliefs, but I will play devil's advocate. Many Mormons view tithe as giving back to the community of which they're a part. And that community, they believe, will provide value to them, in turn. And generally, it does... as far as I can tell from the outside.
Just to clarify, that "Ok, Google" feature requires a Google Assistant device like a Home Mini (or your phone) as the Chromecast Audio has no microphone.