They require darkness in order to shine
Princes use God as a bogey to get their grown-up children to bed when nothing else will any longer serve; which is why they value him so highly. [...] Since that ultima ratio theologorum (final argument of theology), the stake, has gone out of use, the effectiveness of this means of government has much diminished. For, as you know, religions are like fireflies: they require darkness in order to shine. A certain degree of general ignorance is the condition for the existence of any religion, the element in which alone it is able to live.
Arthur Schopenhauer