In this article, we examine the case of Joshua Bell, a famous classical musician. Bell was harmonizing his $3.5 million dollar violin in a DC metro station, and fell victim to what social psychologists call "Helping Behavior."
In this specific case, it was the Helping Behavior of ignoring the musician in the subway, so that they did not feel the need to empathize and therefore help him. Unfortunately for them, it meant that they missed a world-class musician perform 6 classical pieces, making a total of $52.17 from his day in the metro. Only one passerby recognized him, and only 7 in total stopped to listen to him play.
The article uses Helping Behavior as the explanation, getting into why people feel the need to ignore him. His status as playing in the subway in "'street clothes" insinuates that he needs help. Therefore the passerby's ignored the music so that they wouldn't get involved and end up helping at a high cost.
The article explains that people are more likely to help when it's at a low risk or low cost to themselves.
However, it is also possible people didn't enjoy his music.