Because painting ourselves blue turned out to be a tad redundant?
Because somewhere along the route out of Africa, we figured out that wearing skins meant a dead animal who couldn’t provide us with milk, whereas wearing fleece meant a living animal AND more baby animals who could provide fleece and milk?
Because it’s insulating, waterproof, fireproof, and easy to manipulate into textiles?
Because a renewable resource is better than polluting the planet with plastic fibres derived from non-renewable fossil fuels?
Quora linky.