It seems like this new PNG spec just cements what exists already, great! The best codecs are the ones that work on everything. PNG and JPEG work everywhere, reliably.
Try opening a HEIC or AV1 or something on a machine that doesn't natively support it down to the OS-level, and you're in for a bad time. This stuff needs to work everywhere—in every app, in the OS shell for quick-looking at files, in APIs, on Linux, etc. If a codec does not function at that level, it is not functional for wider use and should not be a default for any platform.
I work with a LOT of images in a lot of image formats, many including extremely niche formats used in specific fields. There is a massive challenge in really supporting all of these, especially when you get down to the fact that some specs are a little looser than others. Even libraries can be very rough, since sure it says on the tin it supports JPG and TIF and HEIC... but does it support a 30GB Jpeg? Does it support all possibly meta data in the file?
Try opening a HEIC or AV1 or something on a machine that doesn't natively support it down to the OS-level, and you're in for a bad time. This stuff needs to work everywhere—in every app, in the OS shell for quick-looking at files, in APIs, on Linux, etc. If a codec does not function at that level, it is not functional for wider use and should not be a default for any platform.