That notebook is the fastest most accessible tool to capture my thoughts. I can state concisely what was discussed in a team meeting last october before any notetaking tool boots up. I know kids names, birthdays and favorite movies of almost all my coworkers which I can glance without switching windows while sharing my screen.
the impossibility of such content being legible to anyone else and being shared is a feature I value very highly.
i take it where i want, introspect, take notes. No screen. No distractions. I doodle, draw lines, write jokes, whatever.
Pages on the right are work things. On the left are my ideas. Index on the first page tells me exactly where to turn to for that idea and mockups i had on filling tedious forms.
I know when I'm spinning my wheels. I can see the gaps in my thinking from months ago. I can see patterns in human behavior that I would otherwise have not noticed.
The simplicity is a huge advantage. I stopped looking for anything better. I don't try to promote it either (except on rare occasions). Saved me hours.