Lack of awareness is the main issue by far, but momentum is another. gifs are doing the job and people already have tools they are used to, so there needs to be

Lack of awareness is the main issue by far, but momentum is another. gifs are doing the job and people already have tools they are used to, so there needs to be some compelling reason to switch. For many small animated icons the file-size difference isn't going to be massive and an 8-bit pallet is usually sufficient, and once you start wanting larger animations and full-colour people have already moved to video codecs instead or for non-video-like animations maybe even manipulating SVG. There are no doubt sweet spots where APNG is ideal, or even the only really good option, though I can't think of any that would be common (wanting an animation with an alpha-channel rather than gif's all-or-nothing, maybe). Another matter is compatibility. IE11 is a no-go which even after the recent announcement will kill APNG for some. And while Edge now supports it this has only been the case since the switch to being Chromium based (so the beginning of last year).