There's a difference between taking notes and transcribing, and people who benefit from and proselytize taking notes tend to be very far from the transcribing end of the spectrum. People who are the most effective note-takers tend to synthesize what they're hearing and only write down key points. While the synthesized notes are smaller and therefore faster to write, the real benefit comes from the act of synthesis itself. It forces a level of understanding that the listener wouldn't be forced to attain were it not for taking the notes.

Sadly, there's very little emphasis on what it means to take good notes, or how to go about doing it. I suspect that good note-takers don't even realize that there's a difference between notes and transcripts, so when they promote note-taking as a study tool they neglect to mention a critical step. You probably could become a good note-taker with some practice, and would benefit from it, but if you're not still in school I doubt it would be worth your time.