Because it is not the priority and they don't do VR.
Sony is in VR and they need it and it is a priority for exclusives out of VR and it is possible to market it now because everyone has a headphone and can access youtube. And audio engineers need to fight a lot to make the sound a priority on Sony side. They talked more of audio than CPU and GPU...
Use an headphone you will understand better.
They can use 3d audio in trailers or conference.
I actually use a Beyerdynamic Amiron, a real headphone, so I personally appreciate great audio.
But the reality is that most players out there simply don't have great audio equipment as they use their TV speaker system, some might have some "fashion" soundbar. I surely don't qualify the usual over priced gamer headset produced by some marketing label without any history in headphone design as...good...
To me VR for consoles is a niche market.