"Apple: The First 50 Years", Page 527:
If there were cameras on the AirPod's stems, they could become smart glasses without the glasses. The cameras would see the world around you; you'd speak your questions about what you're seeing; and Siri would speak the answers, courtesy of the visual intelligence technology that's already in the latest iPhones. "What does this sign mean in English?" you could ask. "Who owns this building?" "What is this weird bug?".
In principle, the cameras might also see your hands, watching for gestures that would control your music on your phone.