Let me first point out that I am a PRO-ponent of a universal RAW format. I am not particularly a fan of DNG, but I am all for an open RAW format. Yet I want to present 2 specific arguments that I believe are relevant to the case. These are more plausible arguments why camera manufacturers may be reluctant to adopt a RAW format standard, and might help in understanding the issues better.
Note therefore that this thread is about understanding, not about a pro-con, Canon-Nikon , Mac or PC war. You can do that on several other threads on this forum.
In the history of the JPEG image scheme camera manufacturers were slammed with litigation from patent trolls and american corporations. Not exactly a useful basis for adopting another standard from that country, no matter how well intended...
2. Branded Look
A camera manufacturer has the right to ensure a branded look and quality from their products and in order to ensure that look and quality, the RAW processing pipeline may need to be a closed system.
The general perception of the brand is obviously carried by the entire user base, and, contrary to what you might think, the majority of users do NOT NECESSARILY constitute knowledgable professional or semi-professional photographers with a need to protect their productivity for all eternity through an open pipeline.
Now, clearly, camera manufacturers are free to create a new standard and cater to the need of the possibly small group of users that would actually require it, but I do not believe there is even the slightest chance that Canon and Nikon are ever going to sit at the same table at the same time, to start such an initiative.
Having said this, I do believe that if we can come up with some good arguments to counter the above mentioned issues, then we may have a useful basis for a successful lobby. But continuously shouting about how evil camera manufacturers are or even hinting at torture along the lines of burning toes and feet, is not exactly helping the cause in general.