So...added cost for the camera manufacturer and only cost savings for Adobe. No apparent benefit to end user, other than early adoptors. Possible diminished code efficiency to Manfacturers and also lack of ability to easily incorporate need ideas due to the need to adher to a standard...and as we know, adoption of new ideas to "standards" is a long, winding road.
Yeah, ya know...I'm not going down that rabbit hole with you again. What you wrote above is FUD (Fear, Uncertainty and Doubt). The added cost to the manufacturers? Just how much would a firmware update cost? If you don't know then you are merely speculating that adding DNG would be costly (hint, it would be easy and cheap for Nikon and Canon to do so if they wanted to–they just don't want to).
Benefit to the end user? The beginning of the end of the wild west comes to mind. It took DNG to teach the camera makers how to formulate a sturdy, documented raw file format (Nikon and Canon had zero clues other that what they "borrowed" from Kodak). If the camera makers adopted DNG (even as an option) it would provide end users with options to use a non-proprietary format. If the camera makers' software also supported DNG (which is actually a different issue) it would enable users to use their own choice of file format while still retaining raw image editing. To date, the only camera maker who supports DNG is Capture One (sadly the DNG support is at least 2 DNG SDK versions behind).
"Diminished code efficiency"? Sorry, that is a non-sequitor...those terms are meaningless. What are you trying to say? That Nikon and Canon are incompetent code developers? (if that's what you mean, I tend to agree, they can barely code their way out of a paper bag). But hey, DNG provides a full fledged SDK as a guide to how to do what you seem to think is a difficult task (hint, it would be easy for Nikon and Canon to add DNG) Fact is, current NEF and CR2 files are so close to DNG that all they would have to do is change how and where they write metadata and do so in the properly documented manner (which is spelled out in the SDK in case Nikon or Canon are having a tough time).
So, you think adhering to a standard is an unbearable burden? They already adhere to several standards such as TIFF-EP and EXIF (well, more or less). Would that mean that Nikon and Canon had to play by the rules? Yep...and that's their primary reason for rejecting DNG at the moment. They don't want to play by any rules (and this is good for the industry how?).
In terms of stifling creativity...bullshit (and you know it-you are talking of the top of your head without any real knowledge if the technical implications that are actually involved). Yes, there have been a couple of times that new cameras required changes to the DNG SDK that would have impacted adoption of DNG with a new camera. When Sony first released a camera whose captures could be stored as raw files, Sony bragged about the fact that they had encrypted the raw file data and that it would take Adobe months to decode the file. Fact is, Dave Coffin had already decoded the encryption...imagine Sony's chagrin when they realized how wrong they were (and point of fact, the appreciated the 3rd party raw file format support when it came to selling cameras).
I'm ok if you don't want DNG-your choice...but it would be useful to stay away from stuff you don't really understand and resist spreading misinformation and making uneducated speculations regarding DNG's viability, usefulness and difficulty in adoption.
The reasons why Nikon and Canon refuse to adopt DNG are primarily political, not technical. The cost of DNG adoption would be minimal, the difficulty adopting minimal. Adopting DNG would not stifle creativity nor prevent new sensors and cameras from coming to market. Yes, adopting DNG would require the camera makers to adopt some standards (which I personally think would be a good thing for the industry–for a change). Adopting DNG is free and Adobe has already offered DNG to the ISO for free (Adobe allowed the ISO to adopt and adapt TIFF-6 for TIFF-EP for free, which of course the camera makers are already using).
Look, DNG is simply a well formed, intelligent and fully documented guide for making raw file formats. Yes, it would require the burden of adopting some standards (finally). While Nikon and Canon cling to their undocumented, proprietary raw file formats, the industry continues to suffer from the impact of their rejection of standards. The real secret about all these proprietary raw file formats is the fact that in reality, there are no secrets in the files. The proprietary secrets are in the chips and DSPs that process a raw capture and convert from analog to digital conversion. By the time the capture data is written to media, it's just data. And it's data that Dave Coffin, Thomas Knoll and Eric Chan can "easily" decode (when I say "easily" what I mean is it's time wasted decoding new cameras simply because the camera companies can get away with it–and it's time Thomas and Eric don't have to spend on new processing algorithms).
Personally, I would prefer Thomas and Eric spend their time making my raw images look the best they can possible be rather than wasting time decoding yet another new sensor/camera.
Just so ya know, I'm not interested in getting down into the mud again...let me know if there's anything I wrote that you don't understand but I'm not particularly interested to hearing what you disagree with–again.