Millions of able-bodied American men have stopped working and stopped looking, and two prominent voices spent a Friday night wondering why. Comedian Bill Maher and “Dirty Jobs” host Mike Rowe traded figures and theories on the labor-force exodus during a segment posted to the YouTube channel for “Real Time with Bill Maher.” He pinned much of the trouble on a college system that saddled graduates with debt while leaving skilled work undone. Student loans have swelled to $1.8 trillion, Rowe said on the program, up from $1.1 trillion when he last appeared. Maher floated pornography as the culprit, arguing it strips young men of the drive that once pushed them toward a job and a partner.