All of us were trained in many disciplines, and in one (or two) disciplines in depth.
It is very easy to wrap your head around the idea that you need training to manipulate numbers, mathematical symbols, etc. We also take for granted the fact that we need prolonged training to understand the history of the Civil War or the Roman Empire or understand the geography of regions.
But nobody notices that there is one thing largely absent in our curricula- self-management. How to think, how to make decisions, how to manage your time, how to make yourself be efficient without driving yourself mad, and so on.
Our brains, our bodies were not evolved for knowledge work. We we hunter-gatherers a few thousand years back. The industrial revolution, and the ones came after the first one did not change our bodies or brain. We need to actively learn how to do knowledge-work and learning efficiently.
And this is not modern. Many accomplished individuals had well-thought-out systems to do work. These are detailed in biographies of the likes of Einstein, Da Vinci, Feynman, etc.
Why this was not the phenomena?
Before, a very small percentage of the population even needed to think about these. Because the sheer number of knowledge workers were very very low. Now, knowledge work has expanded beyond the few with no large scale training program available for everyone.
So, this craze on note-taking is merely a symptom of people seeking to solve modern problems in a structured manner.
This is why the Getting Things Done book or Deep Work book gets a lot of mentions in Hacker News books lists. People want to solve these problems.