|Runes cast on a white cloth|
The reason I don't is twofold. First, I don't feel the need to justify the ways that I connect with my goddesses and gods to anyone. Second, I never claimed that this was an ancient approach, though there tends to be this automatic assumption that I believe it to be so.
I am not a purist nor do I try to be. Moreover, I struggle with the idea that I have to be one, because I disagree with the notion that a strict adherence to how I express my connection to the Norse goddesses and gods exists. More specifically, I disagree with the idea that, if I am doing something that isn't accepted as being from ancient times, I am wrong. With regard to the Runes, what works for me is a simple acknowledgement that what I am doing is most assuredly not the exact way it was done in the past, rather that what I do is done from a position of respect.
Comments by Tacitus in his book Germania foster the situation. It is the only known historical reference about casting by Germanic people and there are numerous translations of his description of it. Still, however one translates Tacitus' writing, there is no mention of Runes, only of "cutting marks" into twigs cut from a fruit-bearing tree. We don't know what the marks were or how they were interpreted.
What is especially interesting about Tacitus' explanation is that it has to be secondhand, because he doesn't appear to have traveled to Germania himself. This might help explain the lack of detail in the casting description.
The idea that the marks might be some form of Runes is also brought into question by the fact that Tacitus lived from 56CE (CE = common era) to about 117CE, while the earliest runic inscriptions date to around 250CE. That is not to say that the marks absolutely were not Runes, but it does reduce the likelihood significantly. Then, there is the question of which Futhark was used or should be used. Elder? Younger? Anglo-Saxon? I don't think there is a right or wrong choice.
What do I take from Tacitus? I take facts. Some portion of Germanic people placed a high importance on divination. To divine whatever answers they sought, they cut sticks from fruit-bearing trees and carved marks into them. They threw the sticks onto a white cloth. Someone of authority would invoke the gods, pick up three of the sticks, and interpret them. If the interpretation was disagreeable, they wouldn't ask about it anymore that day. If it was agreeable, they still required a sign of some sort to confirm it.
I incorporate many of these facts into my own practice and I am grateful that Tacitus gave us some insight into the ancient process. However, I also recognize that the interpretations I make of the Runes I cast are based on the Rune Poems (composed in the 8th or 9th century) and that no other evidence for using Runes for divination can be found prior to the 1970s. It would be wrong for me to say that my practice is based solely on historical ritual. However, it would also be wrong to say it is an entirely new age thing. Tacitus provides pieces, the Rune poems provide pieces, and information since the 1970s also provides pieces.
What's most important is that I do not take what I do lightly and I don't expect anyone else to use the Runes the exact same way that I do.