Do you talk about math lectures? Because during my university time I seldom met people, who understood a math lecture during that math lecture. Especially in advanced topics like category theory, algebraic theory, fractal geometry etc. Usually people understood topics and concepts for the first time long after the lectures, often not until after a second exposure in the next course. Also, in many courses you had to take notes, because the lecturer would use custom symbols and definitions. So I agree, taking notes can be distracting, but in most cases it should help your understanding, especially if you lack preliminaries.