Why so little hiring? Make the current employees do it:

A related interpretation, favored by Steven Davis of the University of Chicago, Jason Faberman of the Federal Reserve Bank of Chicago and John Haltiwanger of the University of Maryland, is that companies have reduced their “recruiting intensity.” They advertise jobs but don’t have much interest in filling them.

But it is consistent with anecdotal evidence that external applicants are facing more onerous interview processes and that companies are hiring outside job candidates only slowly and cautiously.

Companies have a certain amount of work to be done to make money. If they can use various pressures to make workers accept more responsibilities for the same money they are effectively cutting costs and making the positions new hires would fill redundant. So they don’t have interest in filling them because it costs money (even before factoring in the fact that hiring and training is expensive). With more to do and the same paycheck it’s a way to decrease workers benefits without decreasing workers benefits.

Overwork can negatively affect an employee’s ability to meet expectations to compete for career advancement, being able to actually take paid time off and cash compensation per real work hour.