Most people don't even take notes or use a shoebox/second brain to store these things. What most lifelong notetakers know is that the notes themselves aren't important, but rather the process of physically writing the notes, internalizing the information, and building new connections in your head is quite important.
The remnants of this process are mostly throw away from the author's perspective, but may be novel to a random person. This reminds me of someone uncovering a journal of nonsensical information saying "What's this about?" to then the author says "That's how I figured it out".
The beauty of it all is that it's meaningful to the author and not necessarily anyone else.