For every Linux power user, there are probably a million regular web users who don't know (or care to know) what a command line is. Web tools are for them.
Why not fork the repo and repackage it as a CLI app if you really want it that way?
People are trying to write software for GPUs more commonly now + because of the troubled GPU programming landscape, it's hard to make programs that work more than one vendor's proprietary flavour of GPU. WebGPU is an attempt to address some of that in browser apps, but it's not ready yet.
Anyways, if you're looking for a cmd tool, rembg [0] is a pretty good one.
[0]: https://github.com/danielgatis/rembg