Adding something in rust into a browser means you now need to bundle all of the needed crates and that your browser now also needs rustc to build… at a minimum.
You also need potentially to audit all the crates and keep them up to date and so on… without crates you can't do so much.
I can see that for components heavily interfacing with high surface area things like encryption, hardware interfacing etc., but why would that be true for a relatively “pure” computational problem like an image codec? Bytes in, bytes out.
You also need potentially to audit all the crates and keep them up to date and so on… without crates you can't do so much.