Women, too, for that matter.
The link is to an article in the Washington Post about an experiment: would people who are accustomed to the average street musician take note if someone of a slightly higher caliber were playing?
In short, no.
It seems to be largely about context. For example, if I were in Los Angeles and happened to run into Gina Gershon at the airport, I'd definitely take notice (and would probably get arrested trying to maintain contact for as long as possible. However, if I were watching a game at Victory Field and happened to see a woman wearing a casual shirt, comfortable shorts and a ball cap, and she happened to look somewhat like a famous actress, I'd be much more likely to give her nothing more than a second glance. Why would I expect to see someone like that in an environment like that?
No one expected to hear a world-class violinist in a Metro station, so even though all the evidence was there, with few exceptions, no one heard one. At most, they simply thought they heard an above-average musician.
I guess I can't blame them. I doubt I'd have noticed, either. I enjoy classical music, but I don't know it that well. I probably would have stopped, though, because I'm rarely in a hurry, and given the chance, I might have figured out who it was.
It would have been embarrassing otherwise. I'd hate to have a former classmate recognize me without returning the favor.