God is pretty much the most famous dad in the world. Even if he hadn’t had a son, he has a fatherly presence in many people’s lives, offering them support and guidance in their times of need.
The famous “Footprints in the Sand” poem, in which a man sees only one set of footprints in the sand when formerly there were two and subsequently asks God why He abandoned him, is a great example of this. And people love it. It’s a great way of conveying the love and support religious people feel that God provides them.
Of course, if that poem really were written by a dad, it might be a little bit different.