Lots of people are allergic to wool. Perhaps as much as a quarter to a half of the population will have a mild allergic reaction if they have ordinary coarse wool rubbing against their skin for a long time, like wearing a woollen collar or scarf while trudging through the snow all day. Some people can recognise whether fabric contains wool just by touching it with their fingertips: an immediate itching sensation. So perhaps it evolved for use by sheep, not humans?