I think buying Trello was great move for Atlassian. No way could Jira compete with them in the long run. And now they are even safe(r) from new Trello-like competitors. Brilliant move for Atlassian. Too bad for us users... :(
With ~350 employees and many mixed teams using only Trello would be chaos. In key areas we need fixed workflows (-> JIRA).
Right now we are planning to add Wekan (FOSS trello clone) to our toolchain for workflows which are more dynamic (less "C follows B follow A" + smaller teams - e.g. innovation and some planning).
Your comment just illuminated that for me and I think you're right. It's the micromanager's dream, but for good managers it doesn't seem to offer enough over the competition to draw them in. The best I've worked with considered PM tools essentially fungible, and therefore weren't likely to invest in 1) paying for the Atlassian suite or 2) the overhead of getting it up and running.
After taking a class and reading up on project management and trying to get more organized about my own projects, it's basically that. People have been able to orchestrate large projects with nothing more than pencil and paper and then typewriter. The best PMs don't need to force a tool choice.
Jira is so customizable and has so many features that it can be made into a sort of bureaucratic prison that's actively counter-productive for everyone except higher-level managers who just use it to generate countless reports. In the worst case, Jira can be used to institutionalize mistrust in employees/developers.
On the other hand, a minimal setup with kanban boards can feel a lot like Trello integrated into a bug database, which can work and scale quite well.
I will say that even a minimal installation of Jira can be overly complex for small teams of 2-5. This is where Trello can really shine.