Another potential problem is that JPEG encoding and decoding is very mature. I remember this being an issue for color spaces JPEG 2000 in earlier versions of OS

Another potential problem is that JPEG encoding and decoding is very mature. I remember this being an issue for color spaces JPEG 2000 in earlier versions of OS X (no idea about more recent versions). No matter what you did as a developer, it never seemed to be possible to get colors to look the same way once they'd been passed through the system-provided JPEG 2000 encoder. If you get all modern browsers to agree to support a new codec, but they all render them slightly differently, nobody is going to use it.