Pamela: mostly because I don't find the arm bend/wrist angles of those setups pain free.
I have a standing desk at the office. A really fancy one, in fact:http://www.focaluprightfurniture.com/the-locus-workstation/
Basically, without a keyboard tray, you're making the height of your keyboard higher (because keyboards aren't 0mm tall, even apple ones ;) ) than the rest of the desk. A keyboard should be set lower than the height of a surface you would feel comfortable writing with pen and paper on.
So... point being, while I'm all for standing, I also worry about my wrists so I want to maximize that as much as possible. I'm willing to go a little not-perfect-ergo when standing (as I don't stand 100% of the time) if I can have a correct wrist setup when sitting.
BUT! you're right. That setup is a lot like what my boss uses (a standing desk plus a tall chair/stoll thing) and he likes it.
Greg Grossmeier at 2014-06-20T19:24:18Z