What fraction of iPhone users do you think have turned off Siri? Based on my circle, it's zero. Android seems a bit more complicated because registration for Samsung or Amazon might be decoupled from device setup, but I'd imagine those are mostly turned on. So most people do have an always or nearly always on microphone in their pocket as the post higher up was trying to point out.
Anecdata, but most of my friends that have iPhones has Siri enabled indeed, but the minority that is aware of the "Hey Siri" feature (the only thing that needs an always-on mic) has not enabled it. Most of them find it creepy.
