Are you an academic researcher? For the variational surfacing, do you know the R&D gap between “Rhino VS. ACIS”, “ACIS VS. Catia” and “Catic VS. XNurbs”? (The original paper is done by Dr. George Celniker, who also was a developer for ACIS.) There are huge differences between academic research and industrial R&D. As @gustojunk said, research software always crashes and may not work for designers …
Since you asked, I give you a bit more explanation: Existing surfacing tools in CAD are just degenerated cases of XNurbs, i.e., disabling energy optimization, generating a fully-determined linear system and only handling simple constraints (mapping 3D curves to iso 2D curves) … For XNurbs, it is the worst case that could never happen. So “in plain English, except for very special cases, e.g., analytical surfaces, for the same input, the surfaces generated by XNurbs should be superior than the ones generated by traditional surfacing methods …” For professional R&D teams from big CAD companies, of course they understand XNurbs’s applications.
While XNurbs is the easiest-to-use NURBS software, some users may only be able to use it in trivial cases, e.g., filling a hole, and within a couple of minters of installation, they can get their design done with XNurbs. They thought they were a master of XNurbs. For experienced surfacing designers, they may spend weeks even months to learn XNurbs, so some users do need the help from experienced surfacing designers for using XNurbs…