If everyone adopted DNG, Adobe's development costs would drop dramatically.
As it is, every time a new camera that does RAW is introduced, Adobe's programmers must code a new interpreter. RAW files are quite complex. They are container files, rather than image files like JPEG or PNG. Within the container, there is a header that serves as a table of contents, identifies the camera, byte-order and so on. Another describes the sensor in detail. There is generally a small JPEG embedded which serves as a thumbnail and/or preview. It can have both a thumbnail and a preview. All the EXIF data. Most importantly, it contains camera-specific data - data unique to that particular model which allows for innovative features as cameras evolve.
Each manufacturer's RAW contents are ordered and chosen by their firmware developers, and can vary considerably from brand to brand - or even within a single brand. This works great for photographers, since it is easy for the company to embed new features, but it is very costly for Adobe to keep up with this. Naturally, they would love to see everyone adopt their standard and conform to its specifications. It is an open, published "standard" that anyone can use. When you realize how much money Adobe would save if everyone adopted it, they don't seem quite so generous or heroic by releasing it.
Needless to say, they encourage FUD (Fear, Uncertainty, Doubt) about every computer in the world suddenly losing the code to interpret any of the RAW formats other than DNG. It could actually happen - if the asteroid were large enough to destroy all computers world wide.
