In short — because the benefits of implementing the technology don't outweigh the development costs, support costs, and risk of fielding a dud to the market.
The Lytro light-field camera was able to capture the rays of the light field hitting the sensor. This allowed for very impressive capabilities, such as determining the plane of focus after the image was captured (i.e., in post), variable post-capture depth of field control, and 3D image creation. Their ultimate photographic camera, the Lytro Illum, was by most counts very promising. There was a lot of interest in the technology's potential, and it was hailed as a potential game changer for several applications of professional photography.
But alas, Lytro shut down all operations in early 2018. For all its promise and features, it wasn't interesting enough to disrupt the existing DSLR and mirrorless markets. For it to continue, tt would have required significant investment in either an entirely new platform (lens mount, lineup of compatible lenses), or partnership with an existing manufacturer. Because they shut down, it's evident that neither of those directions were deemed to be profitable enough to make the necessary investment.
Don't forget, it's not enough to merely have a demonstrably superior product or method. Technologies such as Lytro, ZCam, etc., have to be so superior that they can overcome both entrenched market participants (i.e., the incumbents who have a vested interest in not being disrupted) and the inertia of the installed user base — camera owners who have to be convinced enough to invest not only in new gear, but also invest in time to learn new tools, techniques, and workflows.
Regarding market adoption, there is always a small population of early adopters, tinkerers, tech zealots in search of the next cool thing, etc. But without good tools to manipulate, consume, post-process the new paradigm, compelling content is not created in sufficient quantities. And without existing content, there won't be a consumer demand for new content. It's a vicious cycle.
So you see, that in order to successfully field the type of compelling technology you're talking about, it's not enough to develop the tech. The toolchains, editing suites, data standards, metadata specs, promotional outreach, product support, social media presence, etc., all need to be considered and ideally in place, in order to fundamentally change how we create, manipulate, and consume photographic data.
Based on the fact that even Lytro couldn't succeed with great marketing and media buzz, I'm not surprised that ZCam and the like aren't a regular part of photography. At least, not for the time being.