Imagine you wanted to make a native desktop app that runs on Windows (going back to Windows 95), and OSX, and Linux, and have it use the end users choice of native components, QT, or GTK. It also has to load fast, be accessible, and work on desktop, laptop, and phones. Also, you're only allowed to ship a single binary but you can load in assets based on the device when it runs.
The app could be anything from a single page that renders one image up to a complete 3D game. Users want 60FPS regardless of what it is.
I reckon you'd end up with a relatively complicated build pipeline.
That's what webdev is today.