For two years, Apple's AirPods were a bizarre curiosity. They were clever, but they looked odd and didn't sell very well. Then, they exploded, and according to one source, they have sold more units than even the iPhone at the same age.
The state of play: This will come as no surprise to anybody who has walked down the street or taken the subway in New York of late. AirPods had limited availability when they were first released, but as they became more common, they also started to look less weird. With broad adoption, Apple has managed to re-architect what is socially acceptable and even desirable.