ElfTengu
Blue Belt
My impression is that claiming ninjutsu is actually detrimental to your reputation, and what quality schools that do exist are continuously fighting the poor impression that subpar schools have given the general martial arts community. I'm not involved in ninjutsu directly, but through these boards and others, that's been the gist of what I've seen.
If I were inventing my style and looking for instant "cred", I'd claim MMA or some kind of RBSD over any false association with ninjutsu.
You're not wrong. Many of us who do have a qualification with one of the X-kans which do teach ninjutsu as part of their curriculum, are very reluctant to tell people that ninjutsu is what we do, or even mention the words ninjutsu or ninja when describing it. I call it taijutsu because that's what it is, and I describe it as just another word for jujutsu, which again is not incorrect. Not many people require me to then differentiate between 'my' jujutsu and the Brasilian variety or other sportive versions so it's all good and I can usually leave it at that.
So basically, most of us who do have some training in ninjutsu, do not want to be associated with the term ninjutsu, so it is both amusing and bemusing that so many people who do have never studied authentic ninjutsu feel that they can call their own (usually laughable) antics 'ninjutsu/ninjutsu'.