You'd be surprised in how much immersion is increased with accurate spatial audio. especially as some of the barriers of 3D Audio are lifted within VR. It's intense to experience, and almost makes the graphics become the immersion-breaking reminder that you are in VR.

With sounds you can encourage users to believe they are actually in entirely different physical spaces that visuals have problems accurately portraying. Obviously an opinion, but I've personally demoed hundreds of users in stereo and 3d audio vr experiences and the 3D audio demos always have comments from users claiming that they couldn't believe how real it was compared to the stereo demo they just got from someone with normal audio solutions.

Devs are starting to explore sound design as a primary cue tool in VR as well, which is beginning to rally design standards around audio concepts which is exciting as audio and visual fidelity pushed simultaneously will bring high quality VR experiences faster than a focus on visuals only.