Existing JPEG files (which are the vast, vast majority of images currently on the web and in people’s own libraries/catalogs) can be losslessly compressed even further with zero loss of quality. This alone means that there’s benefits to adoption, if nothing else for archival and serving old stuff.
Funny thing is, there was talk on the Chrome bug tracker of using just this ability transparently at the HTTP layer (like gzip/brotli compression), but they’re so set on pushing their AVIF format that they backed away from it.
systemd maybe, but people are already running Wayland on FreeBSD and OpenBSD