I've recently come alone a few people who like do to their whole creative process on their computer. As soon as the brief comes in, they pull out their computers and start typing down ideas. I ditch the backpack and laptop for a pen and a notebook. It makes for a better ride on the bus for starters. Secondly I find it's better for keeping ideas, I know plenty of computer users that can't find a file. I have all my notebooks on me at all times.
While having a computer would be great for on-the-go editing, I find that when most people write with a computer they will erase ideas they don't like. Losing it forever, you won't remember it, trust me. I also find when you're in a WiFi hotspot, which is everywhere now, they will easily be distracted by the internet. Youtube will play, stumbles will be clicked, and reddits will be read.
Notebooks are not WiFi capable and they're a lot smaller then your average laptop. I can't pull up my email, or edit a photoshop file. But maybe I like it this way. I can still write down all my ideas, where they stay in there forever. If i flip back, an idea can just leap from the page. If you've ever lost an idea notebook, it's almost as bad as losing your laptop. Here is my little collection that's quickly growing. (I used paper and binders first year, ew)