Comment by abe_m

CAD companies are very protective of their file formats, and use that as leverage to "encourage" companies to stay in their eco system, and upgrade to the latest versions of their software.

The main CAD program is often the center of use, and any specialty functionality is a add-in to the main cad program (FEA, CAM, etc).

If the specialty software is stand-alone, it still needs a CAD Kernel to be able to work with the BREP, and there are essentially only 2 main commercial kernels (Parasolid and ASICs).