Knowledge does not exist in isolation. It exists at the interconnection between ideas. Recognizing this fact is the first step toward better learning and understanding.
From there, it is obvious that building a knowledge base where each idea lives alone in its corner doesn't make much sense. Such a knowledge base is dry and provides little value.
While our society and technology changes and improve all the time, our biological nature limits us to a much slower pace of evolution. Our brains are still mostly "designed" for survival. That's probably why we have such a limited short-term memory. No need to remember a gazillion things when the focus needs to be on the danger we face.
Human brains do have an impressive capability to retain all sorts of information, but they're not the best tools available to us. They're not reliable enough. We may work hard and train ourselves to memorize certain information, but there's no guarantee that we'll always be able to find that information back. Memory retrieval is flaky. It's a very annoying issue that we all face from time to time. We also tend to forget a ton of things all the time. And the more we age, the worse those problems get.
Last but not least, when we memorize information, we really have no control over the way that information is structured and stored in our minds. We may remember certain parts of what we're looking for and forget about the most important ones.
In my humble opinion, the main benefit of tools for thought is not the fact that they enable deep thinking, but the fact that they act as a much better information and knowledge repository for ourselves.
In contrast with your brain and independently of the tool you've chosen to use, there's an almost certainty that it will be able to retrieve the information you store in it very reliably. Assuming that you organize, tag and structure your content in a clear, systematic and maintainable way then you should never have trouble finding things back.
All we need for our tools to continue serving us is a clear backup/restore process. We need to ensure that the information we store can never get lost because of technical issues (e.g., file system corruption).
The more information you store and link together, and the more knowledge you amass. The more knowledge you amass, the more value you will be able to get from the tools.
Mort importantly, delegating information retention and retrieval to a tool means that you can sit back, relax and relieve the pressure from your brain. There's generally only a small fraction of what we learn that actually needs to be memorized. For instance, concepts and general ideas. For the rest, Tools for Thought are much better suited to help us.
Personal Knowledge Management is a valuable skill for Knowledge Workers because it can help you understand, learn, and retain more/faster. It can thus help you stay up-to-date and relevant in your field. Externalizing your thinking will let you improve and connect ideas iteratively and incrementally. For instance, each time you go back to a note, you can improve it, refine it, refresh it.
Through the exploration of knowledge and ideas, Personal Knowledge Management is definitely a great way to become more creative. There's a compounding effect too. The more insights and ideas you capture and mix, the more you invite creativity in. As an author and content creator, my PKM system clearly plays a key role for my work. It helps me uncover interesting ideas, weird combinations, topics to cover, angles that I might not have thought about, etc.
It is also wonderful for personal development, as you can explore your own thoughts and ideas, and know yourself better. Through activities such as note-taking and journaling, you can shed more light on how you feel, what you have in mind, what you really want, etc. It is thus a great tool for self-introspection.
PKM is also really helpful for decision-making, as you can better analyze information and come up with more creative solutions to your problems.
I would also say that PKM plays a big role for Personal Organization and Productivity. You can rely on your PKM system to clarify your goals for the future, create plans, organize your work, and review your progress, all in one place.
By managing your knowledge properly, you'll get rid of some issues with the human brain: no need to memorize everything, no need to refresh the information you've memorized, no problems with recall, etc.