Why don’t we hear more about underemployment in the media?

The short answer is—politics. The mainstream media is no longer represented by the independent investigative journalist (although a few of them still exist), but has consolidated into the same kind of corporate oligopolistic empire that controls everything else. Promoting an ideology that proclaims inflation is caused by demand for rising wages and unemployment is caused by an unskilled workforce deflects attention from the real problem—the jobs that are being “created” are insufficient both in number and in quality.