I agreed but these are different mediums. With paper you can't erase obviously, so you use significantly more space when free scratching. Hence the usefulness of the whiteboard.

On a different note, notebooks are great. I converted my wallet into thin Moleskine notebooks that fit in my pocket super easily. I put my cards and bills in it. And I always have a pen in me. Archival pens are great. It's good for doodling too :>