I had spent several years wanting to learn Emacs without actually making much progress. I only really learned Emacs when I had to use a programming language for which Emacs had the best IDE-like experience (Erlang). I think for many niche languages, it's a lot easier (or at least a lot more common) for the developers to offer an Emacs mode than to try and leverage one of the existing large IDEs like Intellij Or Visual Studio. I think it's because, for many projects, a few simple code-aware editing features (syntax highlighting, go-to definition, etc.) and decent command line build tools are enough to suffice[1].

Now that I develop in Java, I definitely use Intellij, but with Emacs bindings. I then use Emacs for note taking, writing shell scripts, etc. I find that this provides me with the best of both worlds in terms of IDE features plus pure text-based productivity (which is where Emacs shines).

[1] Visual Studio Code seems like it's taking over the role of "good enough" editor for languages that don't have full-featured IDEs - a place that's previously been dominated by Emacs and Vim. I like VSC well enough, but I don't think it's Emacs bindings are good enough...yet.