And only one variant of one JPEG protocol ever found widespread use.
JPEG actually published both a lossless and a lossy compression algorithm and accompanying file format. The lossless format faded into near total obscurity, apart from some medical software, where the lossless JPEG data would be encapsulated in a medical (DICOM) container. Technically, lossless JPEG is a mandatory part of the DICOM specification, but not every product (free or commercial) supports it, and it's virtually impossible to find an opensource implementation of lossless JPEG outside of limited implementations as part of medical imaging tools.
There have also been a variety of extensions published to the JPEG lossy algorithm - notably extension to 12 or 16 bit depths. Good luck finding any support for these, at all. Again, these formats were nominally supported in the DICOM standard for medical imaging, but were very poorly supported. A flurry of naive new-entrant machine vendors, ended up embracing these "novel" formats, only to cause total chaos for their customers, as they found that the files were unviewable on incumbent viewing software or untransmittable to other systems.