Sheep were docile, yes, but vigilant. Unlike many people, sheep were always aware that predators existed and were alert for the scent and the schemes of wolves.
Contemporary Americans were so proseperous, so happily distracted by such a richness of vivid entertainments, they were reluctant to have their fun diminished by acknowledging that anything existed with fangs and fierce appetites. If now and then they recognized a wolf, they threw a bone to it and convinced themselves it was a dog.