> Cameras absolutely could emit DNG instead, but that would require more development friction: coordination (with Adobe), potentially a language barrier, and potentially making it harder to do experimental features
I've worked with medical imaging systems from the largest imaging companies in the world -- GE, Siemens, etc. -- all of which use a standardized image format/protocol/etc. called DICOM. DICOM has standardized fields for the vast majority of information you would need to record for medical imaging - patient ID, study ID, image # if it's an image sequence, etc. - as well as metadata about where it came from, like the vendor ID of the machine that did the scan (the CT scanner, MRI, X-ray, etc). There are also arbitrary fields for vendor-specific information that doesn't have a defined field in the specification.
All of these fields have clear purposes and definitions and all are available to every DICOM reader/writer, and yet the company I worked for had a huge table of re-mappings because some scanners, for some reason, would put the patient ID in the vendor field, or the vendor ID in the scanner name field, and so on. There's no reason for this, there's no complication that might cause this; it's all standard fields that everything supports.
These are manufacturers who, while using the standard that everyone else uses, deliberately screw things up in ways that their own hardware and software can silently compensate for but which other vendors then have to work around in order to inter-operate.
In other words cameras absolutely could emit DNG instead, but aside from the arguments that you've made, I have every confidence that manufacturers would fuck it up on purpose just to make it harder for other vendors' software to inter-operate, which would mean that instead of software having to explicitly support e.g. Canon's RAW format, and being able to say "we don't yet support this new format", software would "support" DNG but it would be completely broken for some random cameras because the software developer hasn't had the chance to implement idiotic workarounds for these specific broken images yet.