In the Name of Symbolism
It is commonly understood that symbols are a necessary part of the spiritual path. In ancient and modern texts, you can find many graphic symbols. Sometimes, the texts themselves are symbolic. Such a text uses symbolism to express its message. This means that the themes presented to the reader in these books Generally are never explicitly stated. The Bible, other religious books, and alchemical texts share this characteristic.
Why did they choose to use symbolism? If you want to be clear with someone, you have to speak clearly!
When you buy a book about Theurgy, magic, paganism, or Christianity you expect a book which provides clear explanations and, perhaps, some ritual exercises. Instead, if the author decides to offer you a set of unexplained symbols, you would probably find this disappointing or even unfair.