It helps to prevent moisture, debris, and dust from getting inside of the device. (geekwrapped.com)
In this project, we will go inside some of the devices that we use every day to understand how they work. (edutopia.org)
By pointing the controller's camera inside of the devices, the motion of internal components, likely helped along by IR - reflective tape, can be tracked in three dimensions. (video-games-galore.com)