With tens of thousands of sheep to work their way through in the season, and wages calculated on a per-sheep basis, experienced shearers know how to make their minutes count. They are very Edward-Scissorhands-like with their blades, whipping them back and forth with terrifying speed and precision, leaving the sheep naked, bewildered and several kilos lighter.
But you don't learn that kind of skill overnight and all shearers have to start somewhere. At the hands of rookie shearers, the sheep are likely to get a few nicks and cuts. On the odd occassion, a visit to the vet is in order. These indiscretions are compensated for out of the shearers' wages, so they have plenty incentive to keep damages to a minimum.