Ninja Butler

So the theory goes that Kabuki theater is what popularised the idea of ninjas wearing all black, since Kabuki has Kuroko,  stagehands dressed in all black which you pretend don't exist. And a popular idea, supposedly, is to have one of them suddenly attack and reveal they are in fact a ninja. Thus, people perceive that ninjas wear all black.

It's similar to how in western mystery novels, the butler is seen as just part of the furniture, and thus the butler doing it is seen as a terrible cliche.

Which seems less cool, when you think about it, really.