I'm not well-versed in medieval cryptography, but the vast majority of examples I've seen so far have been state secrets, spy missions (the creation of tactical maps and the collection of information about other cultures), warfare/acquisition-related plans, and correspondence among the nobility that is semi-personal semi-business (since there is nothing completely personal in medieval nobility).
Some of it is recreational cryptography (some enjoyed inventing alphabets and methods) and some is related to secret societies who used it to hide details of their history and rituals.
There certainly was motivation to hide things from the church, especially during the inquisition, but if cryptography were used to do it, it doesn't appear to be as prevalent as some of the other applications. There was also good reason to encrypt trade secrets, but it doesn't appear to have happened very often (with the possible exception of alchemy). Maybe they felt word-of-mouth was safer or perhaps many of those engaged in trades couldn't read and write in those days.
Some of it is recreational cryptography (some enjoyed inventing alphabets and methods) and some is related to secret societies who used it to hide details of their history and rituals.
There certainly was motivation to hide things from the church, especially during the inquisition, but if cryptography were used to do it, it doesn't appear to be as prevalent as some of the other applications. There was also good reason to encrypt trade secrets, but it doesn't appear to have happened very often (with the possible exception of alchemy). Maybe they felt word-of-mouth was safer or perhaps many of those engaged in trades couldn't read and write in those days.