Wayne, the difference is that most of the intelligence that goes into building a camera system is the hardware and the software processing, not the file format.
Cameras that offer non-raw file formats (i.e., just about all of them) tend to use a single one: JPEG. This makes it possible for anybody who has JPEG-reading software (i.e., just about everyone) to read these camera-generated JPEGs as soon as they get the camera, without needing to wait for software updates. For example, you don't need an updated version of Picasa, Firefox, ACDSee, Photoshop, Windows, Mac OS X, etc. to read these JPEGs.
Some cameras do write in-camera DNG raw files. So, analogous to the above, anybody who has DNG-reading software can read those camera-generated DNGs as soon as they get the camera, without needing to wait for software updates.
That isn't the case with today's non-DNG raw files, which is too bad because most use an IFD structure very similar to TIFF; it's just that everyone stores the essential data in different tags (and occasionally move them around from camera to camera ...). And in some cases,
the non-DNG format is quite close to DNG (such as Canon CR2 and some other recent cameras, where the image data format is identical to DNG). Many other cameras are also use delta Huffman coding to store the raw image that is trivially different from the Lossless JPEG compression that DNG uses. So I don't buy the argument that adding DNG support to the camera is really going to cost them more money; if anything it'll save them money.
Regarding your comment "provide Adobe with it's RAW details", you are confusing the image format versus the image processing. It is the image processing abilities (demosaic, noise reduction, lens corrections, tool set etc.), not the file format, where the software should (and do) compete. In other words, ideally, photographers should choose their raw converter(s) based on things like image quality and workflow, rather than what the format of the file is.
It is entirely possible for camera makers to use a common file format without divulging their image processing recipes (i.e., secret sauces) which they could continue to incorporate in their own raw converters (and sell if they choose to, such as in the case of Nikon Capture NX). I would argue that they would actually sell MORE cameras that way, based on the data I've seen.
Gabor, you have now thrown "lousy software architects" and "nightmare of software architecture" in Adobe's direction. You have made some reasonable technical arguments in the past, so I will give you the benefit of the doubt, but the insulting remarks are out of line. Watch your tone, please.