It's where I write all of my personal notes, blog posts, and it's where I wrote both "Game Programming Patterns" and "Crafting Interpreters".
At the same time, it's not the tool I use as an IDE. For programming, I use whatever IDE is dominant for the language I'm working in. Over time, that's been Visual C++, Visual Studio, XCode, Eclipse, IntelliJ, and most recently VS Code.
That doesn't mean to me that I want Sublime to turn into an IDE. I like that it's lighterweight than that. It's the perfect sweet spot for me of rich enough to handle piles of notes and documents and small scale code editing, but not so huge and cumbersome that it gets in my way.