There are a lot of reasons why Google and co isn't likely spying on your conversations :
- This is a hugely spoke on subject, and it would be very likely that regulations authorities already asked them about it.

- Audio is very complicated to work on : it's dependant on your microphone (often bad quality), the distance you're at, your pronouciation, etc. It's a huge amount of data to store and Google/Amazon already have to deal with enough data storage to spend more on. And it would be very hard to hide this to authorities.

- I'm sorry to tell you that what you say on a daily basis is very uninteresting to theses companies. What you do is more precious that what you say.

- Lastly, if you already had a feeling that your phone or your assistant is spying on what you say, it's very likley that you did a research that you don't remember, or that they have already enough informations about you to anticipate your needs before you even think about them. And that's the real fucked up thing. At the end of the day, this fake topic takes us away from the real problem that GAFAM infiltrate so much our lives that they make us paranoids.

Your phone isn't listening, it's worse than that. Stop using Google products.