I think it is for power users who document a lot, just think of it as a better way to organise your documentation. I think the secret behind good documentation is the effort which will go daily to maintain it vs following a specific system.

If you are putting in daily effort you will automatically find a system which suits your needs.

It's therapy for a lot of people. The act of organizing helps them deal with information. That act of organizing and storing can help with recall for me but not as much as writing something down on paper does. The number of times people pull info out of these systems is questionable.

An argument people use is that these systems help you later in life. I find these systems really hard to adopt and also find it difficult to work with people who expose these systems outwardly.