I was talking to a friend recently who is an expert on data security and similar. His take on this is that while we all notice these funny coincidences, it's astonishingly unlikely they're actually
listening to our conversations, because of the enormous amount of data transfer and processing (human or AI) that would be required to
constantly listen to people and then to extract meaningful data from that audio. They're definitely getting stuff from virtual assistant 'conversations', google searches, location tracking, spotify, facebook/instagram clicks, youtube etc.
So, they are totally gathering data about you from a variety of sources but it's unlikely they're listening all the time, or at least if they ARE it's very unlikely they're deriving much of value from the audio. It's potentially even MORE creepy depending how you think about it, that the algorithms are smart enough to recommend things to us that we haven't even searched for.
See this article which basically says the same thing.
https://www.bbc.co.uk/news/technology-49585682
The results won't surprise those in the information security industry who've known for years that the truth is that tech giants know so much about us that they don't actually need to listen to our conversations to serve us targeted adverts.
The reality is that advertisers have sophisticated ways of profiling users.
Location data, browsing history and tracking pixels, for example all provide enough information to predict what you might be thinking about buying.