A "fad"? If so, the "fad" has been around for over a hundred years.
I think it helps a lot of people, including myself. Taking notes helps me stay awake and focused during a lecture; taking notes while reading helps me focus on what's important in the text, and organize it in a way that makes the most sense to me; doing math problems out by hand helps me remember HOW to do the problems during an exam, better than just looking at a correct solution; etc.
But different people learn in different ways, so you may not be in the majority when it comes to learning styles, and there might be a method that suits you better. Also one thing I've noticed about the "writing notes" form of studying is that it tends to take more time than others, so is the benefit from the writing-out itself, or the increased time you spend trying to learn the materials? For example, when I was in law school we were taught to write case briefs to prepare for class. If I had time, I'd write the briefs out on a sheet of paper; if not, I'd just highlight passages and jot a few notes in the textbook. Was the benefit from writing the brief, or from spending the extra time learning the text? I couldn't say.