1. Marginalia. While you can note-take on e-readers, I vastly prefer to do so in physical form. (I'm not entirely sure why, but I know I'm not alone - when I was in college a few years ago, people would print out the lecture slides to take notes on when they easily could have done so on their computers.)
2. Signaling. How else are you going to show people on the subway, in coffeeshops, etc. that you aren't just browsing Instagram and are instead a Very Serious Reader? :)
I wonder if anyone has done studies on writing vs typing vs listening/reading-only baseline.