I'm not completely sure that the vast majority of the guys in the Five Families at the time of Castellamarese were probably not "made" in the traditional sense.

Luciano, Costello, Adonis, Capone... These were just guys who happened to be of Italian/Sicilian stock who rose to the top of the underworld pile. I think that the tradition of "making" only gained prominence once the family lines had been firmly drawn and they had become the national Cosa Nostra.