This explains a lot. Via ScienceDaily:
Within hours this summer, 30 American troops died in a strike in Afghanistan and millions of American investors watched the Dow Jones Average shed an astonishing 634 points in one day. While it might be difficult to find similarities in the two events, social psychologists can detect a common theme: In each case, investments (money and human lives) were made, and those resources were painfully lost.
The ‘sunk-cost’ effect: Untold Americans experienced what is called the “sunk-cost” effect: Less a cognitive thought than an emotional one, this effect is the feeling that they are being wasteful if they terminate a prior commitment. Thus, they pondered: Stay the course and “waste not, want not”; or “cut and run.”
Such a piercing event as suffering the greatest loss of American troops in the nearly 10-year-old war might seem to serve as a catalyst for people to denounce the war and demand a way out.
But a psychologist at Washington University in St. Louis, in what is thought to be the first non-anecdotal demonstration of the “activation” of the sunk-cost effect, has tested subjects and found that highlighting casualties prior to a questionnaire on both the Iraq and Afghanistan wars actually swayed people’s pro-war attitudes rather than discouraged them …
Read more here.