One of the more interesting sermons I heard during my last bout of churchgoing involved the notion that prayer wasn’t necessary because God knows what’s really in our hearts. Per the dogma of Christianity, that’s actually a true point. (Albeit perhaps a surprising one for a pastor to preach.)
It points out a key distinction between theism and deism. In the former, most religions, God is personally involved with us and hears our prayers (God’s responses have always been a different matter.) In the latter, God is not personally involved and doesn’t.
On the other hand, some see prayer as merely a form of meditation.
Despite the title, this post isn’t as strongly related to 
Logos con carne 