> Is there a good writeup about why people want this over other, existing formats?
All the existing JPEG files can be converted to JPEG XL while gaining 20% size and still having all the exact same data. There are, what, tens or hundreds of billions of JPEG files out there for which the "original" (RAW or anything) is long gone (or never existed) and people don't want a "photocopy of a photocopy".
You can even decompress the JPEG XL back to the original JPEG file, bit for bit.
For that alone there shouldn't be any question: it's a wonderful feature.
In addition to that Apple / Safari are going to support JPEG XL and there are huge number of applications supporting that format.
People don't want this "over" existing formats. They want this in addition to other formats.
I'm not aware, but the gist is that it's in some circumstances better than AVIF in size and/or quality. Both of the new formats are wayy better than good old JPEG and PNG, but AVIF is the one Google is pushing.
mozilla didn't remove their jxl support? It's behind a feature flag, like it always has been, but that doesn't mean they will get rid of it or never unflag it.
Chrome team themselves quoted no interest of those browsers as the reason for removal of the flagged code. Seems like an obvious way to pressure Google into supporing JXL would be to get Mozilla to launch their support, together with Edge and Safari?
As a loyal firefox user since the 0.5 release which took 30s to start up, Mozilla is a non-entity these days. It exists solely so that Google can avoid legal disputes. In the mean time, a bunch of grifters have taken over Mozilla for their own financial purposes and push some activist causes rather than a solid browser.