We asked camera companies why their RAW formats are all different and confusing

DNG is easy to adopt so long as your images look like a Bayer image, and you don’t need any special treatment of the raw data.

Sigma’s camera’s are notorious for their lack of support in most editors because their Foveon files require extra steps and adjustments that don’t fit the paradigm assumed by DNGs (and they claim it would release proprietary information if they used dngs).

The bigger issue is that at the end of the day the dng format is very broad (but not broad enough) and you rely on the editor to implement it correctly (and completely). DNGs that you can open in one of the major editors will simply not open in another.

Sigma currently doesn't produce any Foveon cameras - the fp, fp L and BF all use DNG.