Probably portability, it's a pretty good low (but not too low) abstraction layer over the systems preferred graphics API. I'm not a graphics programmer but my understanding is it's closer to vulkan or metal in terms of control over the hardware compared to OpenGL, which has rocky support on Mac now anyways.

What platform do you have in mind (given that WebGPU has at least 2 OpenGL backend, including one that supports WebGL)

I suppose it is just a question of time

VSCode's terminal is rendered with WebGL (a cousin of WebGPU), since VSCode is an Electron app

WebGL is not really related to WebGPU in any way. WebGL is almost a strict subset of Gles3, WebGPU is a completely different API, sharing on a few concepts. They're about as related as Java and JavaScript

They're different APIs, but they have similar goals and benefits: expose native-adjacent performance for GPU tasks in a highly cross-platform API supported by browsers and other host software. The original poster was asking "why [vs native graphics APIs]?", and I think the "why" is the same for both.

Also- VSCode is literally an example of a use-case where you might do this in WebGPU, they just didn't

Maybe building better virtual environments inside the browser