In reality, we do all sorts of things at our desks that aren’t real work (or affect our ability to produce our best work).
We do do a lot at our desks. It's interesting though how much of "work" has spilled onto our other devices. At least during the day I'm in outlook and Omnifocus on my phone. When I have 1:1s with my directs, I bring my iPad with Omnifocus to review goals or notes I've kept track of
Thinking: Nobody does their best thinking sitting at their desk.
I do my best thinking in the shower at home. I've had sooooo many epiphanies over the years in the shower. Either brand new ideas or some problem that may have had me stumped for days.
I think it's the sensory deprivation. There's nothing to distract you, your mind is free to wander, and there is plenty of ambient noise. Sing if it helps!
This doesn't work as well for me in the shower at the gym. I'm usually rushing to let the next people in or to get to work, and the water temperature is usually lukewarm or cold to help me cool down. Anything I can help to do stop my sweating before work.
Socializing
I think a standing desk hurts me on this regard. I notice that more people come up to me to chit chat than if my desk is down and I'm sitting