What is keeping them is that even the original version is labor intensive.
Most people are forgetting that ZK is a tool to organize knowledge for the purpose of writing papers. When the craze began a few years ago I dove deep into it and discovered a few things:
- 95% of people/sites talking about ZK are not following the ZK principles (atomic notes, with forward and reverse links).
- It is time consuming. When you write a new note, you have to put in the effort to make multiple notes to make them atomic, and spend time figuring out the appropriate links/chains to insert them into. This often requires examining a lot of previous material you've written to ensure there is not much overlap. It's a much slower note taking process than anything else I've used.
- Those that do follow it say you need to stick to it for a long time (at least a few years) before the gains start to compensate for the labor. I recall one particular academic who started doing ZK during his grad school years say it took about 8 years of following the ZK discipline before it began to pay off (and it keeps paying off years later). Think about it: All the knowledge accumulated stored in the form of ZK notes, and it didn't pay off until quite a bit after his thesis defense.
I don't doubt ZK is worth it, but I simply don't have the time. One has to factor in opportunity costs. Unless you plan to become a prolific writer/essayist, I would not recommend this approach.