It is not only the fact to be able to write all over it (although it is a huge one), but there is something about the haptics and spatial distribution of information on paper that makes me remember content better. For example I know a certain formula was on the lower right hand side of one of the last pages of an article. On the other page was a graph.

That way I retain and find information much easier.

With digital content it is all a blur on the same mini screen of my smart phone.