Within the note-taking and personal knowledge management space, there is a question that gets thrown out as jab: But do you have a serious context for use?
In other words, why are you collecting all of this stuff and writing all of these notes? The implicit claim here is that you are wasting your time if you're not taking notes for a clearly defined, externally validated purpose.
At one level, my answer to this question is really just "life". I live in a world where I play, work, worship, invest, vote, learn, teach, and plan. Oh and I have a family that is directly affected by my actions and decisions. Seems pretty serious to me.
But to make it more concrete: There are practical problems in reading, learning, writing and teaching that require note-taking skills.