Mostly because of bandwidth and physics. You have to get information into the display in a form that the display can convert to spatial/angular/wavefront information efficiently and with enough fidelity to be believable.
Any data compression method has to be compatible with the underlying display technology so you can bring the signal straight into the modulator. In addition, there's a wire problem: you can only bring so much signal into a light modulator because the signals interface through a surface, not a volume.
For these reasons and others, true holographic displays are simply not competitive at this time with stereoscope-like VR systems, which rely on tried-and-true, market-driven incoherent-light raster display technology.
People have been asking these kinds of "why not" questions about 3D and building various types of 3D display technology in garages and labs for almost two hundred years. With the exception of the discovery of optical holography, it's surprising how much is fundamentally unchanged.
Any data compression method has to be compatible with the underlying display technology so you can bring the signal straight into the modulator. In addition, there's a wire problem: you can only bring so much signal into a light modulator because the signals interface through a surface, not a volume.
For these reasons and others, true holographic displays are simply not competitive at this time with stereoscope-like VR systems, which rely on tried-and-true, market-driven incoherent-light raster display technology.
People have been asking these kinds of "why not" questions about 3D and building various types of 3D display technology in garages and labs for almost two hundred years. With the exception of the discovery of optical holography, it's surprising how much is fundamentally unchanged.