Mind Maps are basically digitized "brainstorms" that we were all (some?) taught in school. Digitizing anything comes at a cost: Using the UI. Usually pencil and paper is way more freeform and faster, but having your ideas digitized has some intense nerd value!
No not all of us were taught this in school. Also there are mind maps and mind maps. Tony Buzan is the man for the classic mind mapping techniques but people should try to evolve their own and like myself will often develop their own shorthand in the process which makes note taking and mind map design so much easier.