After all the column inches dedicated to Sony's explanations as to the inclusion of a light bar on the PlayStation 4 controller, it's only now the real reason has been revealed: it's part of Project Morpheus' tracking system.
As the VR tech was a secret at the time, it simply couldn't be acknowledged. The connection to the VR device came to light during a talk between TechRadar and Senior Designer at Sony Computer Entertainment Europe, Jed Ashforth.
"The tracking light... it was our department that said we need that on," he explained. "It was for tracking for VR.... we couldn't tell anyone what it was for."