"Some of it is also concern about how you are going to be viewed as an employee — whether you can be counted or not. Whether by having too many sick days, too many absences, you are not seen as reliable. At the very core of being American is the idea of being a hard worker."
From a BBC.com article titled "Why Americans don't take sick days" — apparently prompted by Hillary Clinton's soldiering on despite whatever it is that's ailing her.
Hillary aside, it is something we Americans do, no? Years ago, I had what was eventually diagnosed as pneumonia. I still taught my classes, including a big Evidence class, where I can remember getting into a coughing jag that just wouldn't end. The students all just sat there, impassive, waiting for me to come around and get back to what I was supposed to be doing. When I finally went to the doctor and got the diagnosis, I asked what to do, thinking I'd be told to stay home for some amount of time that I would need to deal with and prepared to picture myself at rest. But the doctor told me I should go to work. That is, if I thought I really should be staying home in this condition, I didn't have a doctor recommending that. I'd be malingering.
The American work ethic is crazily intense, to the point where otherwise competent people worry about not just doing their work but looking busy. And institutions of intelligent people devise ways to observe and take account of just how hard you are working, thus motivating people ever more to the idiotic enterprise of looking busy.
Meanwhile, to quote Colin Powell's email: "[Hillary] is working herself to death."