Am I missing something here? Is there still something Adobe proprietary about the DNG format causing for example Phase One and Leaf to avoid it, or perhaps they still see some reason to lock in photographers in their formats? Maybe Phase One might want own formats to give Capture One a stronger position against Lightroom?
One reason that I have heard mentioned [and was also 'unofficially stated when Apple did not support Flash on the iPad] is that adhering to the DNG format ties you, as a developer, to the whims/ decisions of an outside company.
Let's go through a basic scenario:
1) Adobe modifies the parameters for DNG
2) the revisions breaks the compatibility of your files to the most recent version of Lightroom
3) the issue is brought to the attention of Adobe Lightroom devs
Two basic outcomes:
A) the issue is resolved with the next update to the software
B) the issue is on the schedule, yet to be resolved
For (A), this means that there is a span of time where your device is NOT compatible with the latest version of a popular software. I leave it to you to extrapolate what this can mean to current [or potential] sales of whatever you're making. The most obvious example in the not so recent past is to look at the contortions Apple went through to get continued Microsoft Office support for OSX [when Apple was on shaky financial grounds]
For (B), this means that you future products might be bound by issues other than only software issues. One example might be political, where continued support is dependent on an unrelated action: like QuickTime on Windows [again, many years ago] being threatened by unrelated politics.
"In his testimony, Tevanian outlines how Microsoft pressured Apple to make Internet Explorer the default web browser on the Mac for a period of five years. If Apple had said no, Microsoft would have pulled the Office suite for the Mac, which would have torpedoed the platform. The testimony also details how Microsoft pressured companies like Compaq and AVID to not use Apple’s QuickTime technology,"
By no means an I saying that the above reason are the only reasons why any digital camera manufacturer develops and maintains their own code base and proprietary formats. Thought I have heard, every one in a while, why a company would not want to outsource a very fundamental part of what makes their product reach a particular quality of result.
Owning the whole experience is the best way to control the quality of the product you provide/ sell. Like the reason Apple developed the Apple Stores.
/there are other reason, also