What might be a purpose of such encoded notes?

The primary purpose of encoded notes is to protect information or convey secret messages. When information is encoded, it is transformed in a way that makes it understandable only to those who possess the key or method to decode it. This technique is often employed in various contexts, such as espionage, secure communications, or even personal notes where the writer wishes to keep the content private.

While coded messages can sometimes be entertaining, that is not their main intention. Similarly, summarizing events or presenting clear ideas typically involves straightforward communication, which would not necessitate the use of encoding. In contrast, encoding is specifically designed to obscure the content and safeguard it from unintended recipients, making it essential for transmitting sensitive information securely.