JPEG XL on the web does not arrive there ex nihilo: there is a production pipeline that creates and puts files on web servers and points to those files in HTML

JPEG XL on the web does not arrive there ex nihilo: there is a production pipeline that creates and puts files on web servers and points to those files in HTML tags. That production pipeline may also be used to generate images for things besides the web, so the creators have the choice of having one set of files used everywhere, or one set for the web and a second set for other things. That JXL lossless is overkill for the web may be overridden by the fact that people don't want to deal with the hassle of multiple sub-sets of files (i.e., laziness or "efficiency").