They probably put it in to do gaze tracking in the hopes of selling that data back to movie studios/advertisers. I'm not sure if they currently sell this data, but I'm sure we will find out when/if some disclaimer flashes on the screen in the beginning of the flight.
Hopefully it doesn’t catch on too much. I’d boycott any airline that I knew was doing that.
Would security services pay for good 3D scans of all people taking airline flights. Seems a possibility to me.