How different would your life be if you never forgot anything?
Anything you read, any ideas you have, names of everyone you meet, everything you learn.
How much better would your life be? What opportunities would you have? How would your work improve? How would your relationships improve?
This is the ultimate goal of a personal book of knowledge.
The tools are getting better every day. Once there is an AI layer on top of a PBOK it will become your own personal assistant/life coach.
It may seem far-fetched, but think of what things were like only 10 years ago.
My advice is to start your PBOK now so you are ready when these newer tools come.