Main problem is, religion remains a hugely important force in human society. Between Christianity, Islam, and Hinduism, two-thirds of all human beings are religious and at least partially theistic, and more than 83% follow some form of religion (whether or not it is theistic, e.g. Buddhism or various non-theistic folk religions.) Gods and faith are a staple of fantasy literature; to ignore them completely is likely no more tenable. Compromise solutions like 13A's approach are probably the best of a bad bunch. In 13A, there are two groups of deities: the Gods of Light and the Gods of Darkness. The former are the "good guy" deities that most characters revere, the latter are the dangerous/evil/corrupting ones that want to rule. Neither are ever specifically named nor enumerated, and the narrative keeps them both at arm's length to avoid excessive entanglement. Thus, the gods exist, but they never get particularly involved in anything unless DMs (and, ideally, players) specifically want them to.
The space usually taken up by deities is instead filled by the Icons. This serves the double purpose of keeping overt religious components out of day-to-day play, and making sure that the "movers and shakers" of the setting aren't at the enormously-cosmically-powerful deity level, but instead relatively mundane and even killable without upending the setting. The loss or altering of an Icon is a major, perhaps even age-defining event, but it's not something that will cause the world to end, generally speaking.
