It isn't simply the functionality, but also the massive community/examples/tutorials/etc that already exist for the JavaScript/Node/Electron ecosystem. WPF, even on Windows, is much smaller but if they ever ported it to Linux/MacOS/iOS/iPadOS/Android the resources would be microscopic, and it would be a legitimate limiter to the platform's success.
It would largely be dead on arrival. I wouldn't even use it (and I am their core developer demographic). The only argument people can make is performance, and WPF isn't exactly speedy itself (particularly without hardware acceleration). Plus you're competing with a much better ingrained Qt.
I was actually trying to create a cross-platform solution this weekend between PyQt and Electron, and ultimately wound up using Electron, not because it is better within itself but because you have this huge ecosystem of samples/snippets/etc to built upon. It is a productivity multiplier.
- An Electron application is necessarily slower and larger than a native application with the same functionality
- An Electron application is yet another browser instance on a user's machine, with all the vulnerabilities of that version of Chrome
Those two alone are enough reasons for a lot of (but still far too few) developers.
Software is getting slower much more rapidly than hardware is getting faster, and one of the reasons for that is Electron and how seductive it is to application developers.
It's a bit of a shame, because I strongly suspect the theme is easily overridden. It just needs a designer to make a consistent set of controls.
I wonder if some design work could be crowd-funded.