@jaffathecake I mean it's mostly about adoption and compatibility, I believe and because of macOS JpegXL already has a lead over Avif in terms being supported in programs like Affinity of Photoshop.
Ease of adoption seems to be symmetrical: it's very easy to support Avif for a web browser, since it has to ship a decoder for video anyways, yet most publishing tools don't already do that and seem more comfortable including JpegXL instead