Voynichese is a numeric cipher?

[ololololo]

I'm not sure why we treat 15th century human beings as purely rational creatures that would only do things in a utilitarian way

Oh, I remembered You are not allowed to view links. Register or Login to view.. They work very quickly, but unfortunately, they’re impractical to use.
Overall, you’re right that a person is capable of anything, but it’s important to understand that, taken together, creating a single book cipher is incredibly difficult. And if we’re talking about a cipher (which means we’re implying the purpose of encryption), then we come to the point that complex ciphers are impractical to use because they’re redundant.
It’s the same as if you were preparing a culinary masterpiece for breakfast. You may want to do it, you may be able to do it, but your laziness will convince you to order a pizza...