There isn't one and there never will be because people like different things.
Why do people like you constantly say "what's the killer app" ever time something new VR comes out? I've been doing VR since oculus dk1 and VR has been crazy enjoyable from time to time. VR is cheap as hell now. Quest2 was $300 for quite some time even before the Quest3.
If you can't find enjoyment with virtual reality from a $300 stand alone device that's a you problem.
It’s asking for the use case. If there isn’t a use case outside gaming, there is no value on the table for non-gamers.
You can also roam using apps that let you do Google street view stuff in VR, create art, watch movies in a theater like experience alone or by yourself, and of course a lot of people use it for porn.
Even usual non-gamers love stuff like Walkabout Mini Golf or Star Wars Pinball.
What portion of that market is VR?
That’s the issue I see. Gaming may be the best thing in VR, but VR hasn’t felt necessary to the average gamer at all. It’s still a small niche.
So what? Go play and enjoy.
>VR hasn’t felt necessary to the average gamer
Not even sure what that means. You come across as someone who likes to complain and never actually enjoy something. Good luck with that.