Really, who needs optical for audio? If you could connect the PS4 with component or s-video I'd understand, but as HDMI carries sound also, the optical out is just totally redundant.
Only if you'd connect the PS4 direct to a projector and need to route audio to an older receiver that has no hdmi, then I see the need, but that's a rare case.
Only if you'd connect the PS4 direct to a projector and need to route audio to an older receiver that has no hdmi, then I see the need, but that's a rare case.