Interesting question. I think there are three key reasons for why editors don’t often engage with Discussions.
1. Product limitations
2. The nature of wiki editors
3. Legacy reasons
The way Discussions is currently built makes it fairly tucked away in the desktop world. Unless a wiki chooses to embed a Discussions feed module somewhere, the only connective tissue between a wiki and a Discussions is the Discuss button in the page header. Because of that, there’s an element of it being out of sight, out of mind. That’s contrasted with the FANDOM app, where the wiki and Discussions are much more unified. Discussions is surfaced more in the app, and that’s why most Discussions users are in the app.
In regards to the nature of wiki editors, editors are often a much different type of user than someone who wants a commenting experience. Wiki editors often contribute long-form, in-depth, and highly researched content. A commenting experience is much more lightweight. On the one hand it would be easier for a wiki editor to enter Discussions than for a Discussions user to enter wiki editing, but often times the interests don’t overlap.
The legacy reasons are that FANDOM used to be only a wiki farm, and there are a number of people who have been around for years that view the platform as being one that should exclusively be for wikis. Discussions, as well as FANDOM.com editorial and other features, is sometimes viewed as a distraction from that original wiki-exclusive purpose.
As for me, I set up Discussions here in its earliest incarnation in preparation for The Force Awakens. I was active probably for a few weeks, and then turned things more over to community members. I came back as a result of some of the ongoing issues, and now I’m sticking around for the foreseeable future!