Implementation will be hard. Having the mic on all the time drains battery. Storing the data offline and uploading discreetly when the device is plugged in will be discovered quickly. I think on-device voice recognition has come a long way nowadays so with more powerful phones, one of the big companies might try this soon.

It’s exceedingly unlikely to be this kind of conspiracy and far more likely someone from the same IP address looked up related information.

Siri can't even tell if I'm saying "apartment lights" or "Obama lights" when I'm talking directly to it. And if it's not even hard enough to transcribe all the ways all the people across the globe might pronounce words in all of the languages they speak, there's the problem of deriving who said it (was it you or was it the TV?) and deriving what was the expressed sentiment.

It's so much cheaper and technologically easier to parse your browsing history and parsing things you enter in as text than it is to parse voice. Especially when you don't own the platform your software is running on (what would need to happen for Apple to allow Facebook 24/7 access to the iPhone microphone)?

Also, Google/Apple/Amazon/Facebook don't have to respect our privacy, but they do need to respect privacy laws like the GDPR, so they can't actually tap your voice without your consent unless they want to risk actual billion dollar fines.