what steve says is all partly right, but in the case of Sister Act, most of the musicians are fiddlers, and I've an idea that, in childhood at least, it's easier, has more street-cred, for a girl to be a violinist/fiddler than a boy. So in a way girls have a head start. Besides, most folkies (well the ones who are replicating traditional stuff more exactly, anyway)learn partly from playing along with their elders, at least to start with, rather than paying with peers solely. And some young women are able to withstand the social pressures to completely fit in with their general peers long enough to find a like-minded musical peer group to belong to. (Am I rambling on? Yes, probably, soorry D & J!)