Why haven't volumetric displays taken off?

I see volumetric displays at conferences, in advertising, and super niche use cases.

It's usually something like the Voxon or Hypervsn, or some lesser known fog display.

It looks cool in person. Not sure if it's too expensive, hard to use, or just not solving a real problem.

But I'm curious why hasn't this stuff taken off?

Are volumetric displays a dead space? Is anyone on HN working on this stuff or seen anything interesting in volumetric display tech?