DWG file format is a proprietary CAD file format created by Autodesk many, many years ago. Most CAD applications and hardware rely on this format, including apparel CAD. The proprietary software that I use on a daily basis uses the DWG file format. Providing support for the DWG file format in free CAD projects is critical in order to provide needed cross-compatibility with other CAD packages. Unfortunately, there are some major issues that have to be worked out. There is an excellent article explaining the history and current problems of the DWG file format at the libregraphics blog.
I'm following the lead of librecad in the direction of licensing, so at this point DWG can't be incorporated into sodaCAD.