I can think of a few further purely speculative inferences. Clearly, somebody created the divination systems used in various cultures throughout the world. The Xunxi quote gives reason to believe that for some members of at least some cultures, systems of ritual, perhaps including divination, were perceived as something like a useful technology. With perhaps daily use by a number of practitioners, possibly engaging in ongoing intergenerational discussions about the efficacy of their divination system, it might have been subject to many optimizing tweaks.
The I Ching does appear to have different versions. From Wikipedia: “Various modern scholars suggest dates ranging between the 10th and 4th centuries BC for the assembly of the text in approximately its current form” (emphasis mine). It seems to me that anyone telling fortunes for a regular clientele will stay in business longer if their advice offers at least the appearance of utility. Royalty might have been more educated and more sophisticated consumers of divination; perhaps they knew exactly what they were buying. After all, if it’s possible for divination to offer both the mere appearance of utility and the real thing, all else being equal we’d expect the latter to drive the former out of the market.
When I synthesize the posts of Vaniver and Said Achmiz, it seems to suggest that divination is useful both when random and when the answers have an optimal wording and frequency distribution.
Given that different societies will feature very different pressures and power structures, it seems unlikely to me that a system of divination optimized for one culture (or segment of that culture, such as royalty) will necessarily translate with perfect fidelity to other contexts. It may not even optimize the conscious goals of the individuals using it, or the survival of their societies as a whole.
I can think of two ways divination systems might be retained. One is through conquest. If they promote that activity successfully, it might lead to the spread of the divination system. Another is through promotion of individual flourishing. If a divination system helps people achieve their aims, they might continue to use it, teach it to their children, promote it among their friends, and be imitated by their enemies.
I’d expect a system that does both to be most successful, and my mind immediately jumps to the dual nature of many religions, which are by turns warlike and peaceful. Though the “doves” and “hawks” of each culture or religion often seem to despise each other, they may very well work synergistically to promote the spread of their shared culture. The “hawks” promote an attitude of conquest and hardline defensiveness, while the “doves” promote the benefits of a focus on peaceful individual flourishing. Both can be useful propaganda tools both within their own borders and to outsiders. In order to be convincing to others, they need to be utterly convinced themselves that they are rigid hawks or committed doves. A savvy leader would known how to make use of both.
This is getting a bit away from divination at this point, so I’ll leave it there. I do think that any account of the utility of a divination practice (or other cultural practice) needs to explain for whom it provides utility and the mechanism by which it does so. That’s the reason for digressing into my “hawks and doves are best friends” theory. My guess is that even when a religion doesn’t have an obvious divinatory practice, that it has other ways of accomplishing something similar.
I’m less familiar with Island and Judaism, but in Christianity, it seems to me that sermons, rotating selections of the Bible chosen for study, prayer, and calls to take these words and rituals to heart in ways that are personally meaningful for the congregation are somewhat “random”—or at least out of the hands of the congregation unless they’re willing to change churches—and optimized, as judged by the size and growth of the congregation, or the success of cultures that and their varied practices.
It would be interesting to speculate on how much the physical form of the randomization practice or any reference text/image plays in the efficacy of these practices. Can yarrow sticks be replaced with a random number generator, if we’re aware that’s all that’s happening? Or would that make it less effective? Perhaps there is some aspect of human neurology that makes divination done with certain physical implements more compelling than that done with others.