The people who believe it’s listening would never accept even the most ironclad “proof” that it’s not. This is a hallmark of conspiracy theorists. So why bother?
I believe it's listening based on an overwhelming amount of anecdotal evidence reported all over the Internet. (Where there's smoke, there's fire.) Including by intelligent, scientifically-minded people. At the same time, it wouldn't take much at all for me to believe otherwise: a simple blinded test where some people leave their phones in a room, researchers come and talk about some subject (absent the owners), then…
This is exactly why I believe pizzagate, am a 9/11 truther, etc.