https://techcrunch.com/2019/01/24/hidden-screen-in-ios-12-2-beta-hints-at-airpods-that-can-handle-hey-siri/

It’s a weird quirk of the current generation of AirPods: they support Siri, but only if you double-tap one of the earbuds first. Unlike with iPhones, iPads, Apple Watches and HomePods, you can’t just say “Hey Siri” and babble out your request.

Rumors have been floating around for a while suggesting that a new iteration of AirPods — AirPods 2, the rumor mill is calling them — would bring “Hey Siri” functionality. Now a screen hiding in the latest iOS beta seems to suggest the same.