Not OP, but a pretty common reason is having a super-modular and hackable IDE that can be used to develop pretty much anything. Everything is JSON-configurable, all editors are webviews, so adding stuff like HTML rendering in Jupyter notebooks is almost trivial from a technical perspective. Fleet might be a step in the right direction, but still feels like a layer on top of IntelliJ, which is a beast in of itself, plus it is closed-source.

Also the approach of decoupling editors from the language support via LSP might be one of the biggest innovations in this space in recent years, IMO. Having a widely adopted and open protocol for language support effectively made Neovim, Emacs etc. a viable choice. It has spawned several high-quality LSP implementations, often directly supported by the compiler vendors, e.g. clangd or rust-analyzer.

Arguably Microsoft has been monetizing a bunch of services on top of VSCode too and they haven’t always stuck to their own principles (see Pylance, a closed-source language server that only runs in official VSC builds), but the LSP itself was still a pretty big net positive.

Swift does, though using the dollar sign rather than underscores

That article tells you how to set up syntax highlighting and run the command-line compiler by hand, not really comparable to IntelliJ… The article feels like a generic SEO post

Just wanted to point that rust-analyzer is the fantastic language server that powers the language support, and it runs in a lot of editors (VS Code, Emacs, Neovim, …)

Did you focus the popup containing the Touch ID symbol? Often times it opens defocused and you have to click it to actually use Touch ID.