Difficult to know who started it; I suspect that it's started innocently enough, with somebody turning up with artifically-curled hair, and others copying it. Then perhaps some of these girls have got better marks, and the suspicion has got about that it was because of the curls, so then everybody has felt that they had to do it to compete. And so on. But there's a definite idea that it's now become a requirement (see some of the comments in previos posts). It certainly isn't being discouraged by the judges.
John Kelly.