There is a lot more audio codecs embedded in other things than there ever were personal music players, by orders of magnitude. Vorbis was ubiquitous in video games, for example.

Personal music players had the issue that they had to have MP3 due to market forces, so offering Vorbis didn't save them any money. There were also some design decisions in Vorbis that made it a little more annoying to support on some very limited hardware than MP3.