Because I can take the pages out not only to rearrange them but to run them trough my typewriter.
I love how authentic and kind of messy a typewriter looks. I love to use it to break up the monotony of my cursive handwriting. Typewriters also make me nostalgic for the letter writing days of yesteryear.
If you don't have a typewriter but love the look you can go to font websites and download typewriter fonts for free. I've used Dafont a few times with great success.