Wikipedia: Folk music - loss of musical ability in the community said:
In nability to sing is apparently unusual in so called traditional societies, such as the Urarina of the Peruvian Amazon. Among the Urarina, one notes that the customary practice of singing folk songs, shamanic chants and myths begins in early childhood (See Bartholomew Dean's forthcoming, Ambivalent Exchanges: Urarina Society, Cosmos and History in Peruvian Amazonia. University Press of Florida, 2007, which represents the first book-length ethnographic of account of Urarina society, culture and shamanic resistance).
This in turn democratizes musical expression, and as such everyone gets the practice needed to be able to sing at least reasonably well. In the absence of traditional or folk music, many indigenous individuals do not sing (see Bartholomew Dean 2004 “digital vibes & radio waves in indigenous Peru” in Indigenous Intellectual Property Rights: Legal Obstacles and Innovative Solutions. (ed.) M. Riley, 27-53 New York: Altamira Press[1].
In some instances, it is possible that non-singers feel intimidated by their widespread exposure to recordings and broadcasting of singing by skilled experts. Another possibility is that they simply cannot sing, because they did not learn to sing when they were small children, the time that learning of cultral orality takes place most effectively.
As recently as the 1960s audiences at U.S. sporting events collectively sang the American national anthem before a game; the anthem is now typically performed by a recording or a soloist.