It's a child of the 60s and with all that was going on quite fitting in that timeframe. Since then it's been corporized with trainers worldwide going for certifications to be allowed to use the name. (Another sign of the time, this time more modern.) They won't change it due to their organizational structure. It's sort of like a brand office with a lot of freelancers on the side. What further strengthens this is that they seem to think Marshall Rosenberg is a hero and he is still alive.
I actually love NVC, went to several trainings where I was quite the outlier and had to swallow twice before asking my firm to pay for it. A more corporate branding would be benificial for my part of the market.
Less qualitative (imho) communication theories get pushed by corporations I've worked at, but the main selling point is that these courses are integrated. You get a slick trainer or two, they use actors for sessions, they have shiny branded materials, perhaps a website for a brush up training afterwards. NVC as far as I've seen it appeals to those with a less corporate affiliation, works with books external to the course (a lot of them) which might feel to an outsider like some quasi-scientific appeal and with themes that seem childish. I had no problem with the giraffe once I understood it, but no corporate trainer has ever tried to have me wear giraffes ears in front of my co-workers. It feels like good content, scientology method.