Then why don't they investigate wage theft? Googling around suggests that the cost to the US economy is about the same as shoplifting (and I'm guessing individual cases could be much higher value than shoplifting). When was the last time a battering ram was used in pursuit of a wage thief? Or when was one even arrested?

To answer my own questions, police do not care so much about the "value" of the target. Their behavior is much easier to explain once you realize that their job is to protect capital.