I'd guess that it is mainly selection bias. We have all heard of Mozart, ListLiszt, Bach, but never heard of SaliarySalieri, Emile Bernard, or Khosrovidukht. Similarly, we have heard of Pachabells CannonPachelbel's Canon in D, but not Als der gütige GottAls der Gütige Gott even though they were both written by Johann Pachelbel. Art tends to survive only when it it is good.