Lots of reasons: No big company has pushed it yet. Battery constraints. Processing constraints. Space constraints, no one wants to look like a cyborg. Software

Lots of reasons: No big company has pushed it yet. Battery constraints. Processing constraints. Space constraints, no one wants to look like a cyborg. Software to make it useful is in itself a large undertaking. Making ar reactive the surrounding requires really good machine perception. Which required good sensors and large batteries and powerful processors. It's coming but everyone is waiting for the tech to be ready.