I mean, really, why would it be encrypted?

[davidjackson]

Many of us make use of file encryption when storing sensitive information. Why would not a medieval person follow that same concept?

File encryption is easy and automated. Plus, we are all reminded on a daily basis of the dangers of information security.
Encoding folio after folio in an unbreakable code 600 years ago neither fits in with real needs, nor mindset, nor physical capabilities.