I'm convinced that most of the long hours of corporate America can be explained as a form of signaling. This is just more evidence that there are a whole lot of bullshit jobs out there. [0]
Anecdotally, when I worked as an investment banking analyst, there was hardly anything to do from 9-5, then 6-8 hours of work was dumped on my desk at 5pm. Half of that work was un-doing changes I made the day before because the VP on the team didn't like the updates the Associate wanted. Organizations are set up to be inefficient in order to signal how serious they are and what hard workers they have.