They are absolutely listening. This is very easy to test. Speak around a Google or Amazon or Apple device, and start talking about things you would never buy, never need, have never looked up, and is completely irrelevant for your demographic. You’ll get ads for it anyway by the end of the day or week.
Listen to the Big Tech comments to press and congressional testimony very carefully. They always say something like, ‘Facebook is not spying on your microphone.’ They’re always very carefully wording it as the parent company is not listening to your devices. But they absolutely know either one of their subsidiaries or their partners are listening to your microphone, and feeding the data to them.