No surprise here!
LOL, I saw this coming from a mile away. OF COURSE Google is going to spew ads through this.
You basically put a piece of hardware in your house that is dirctly connected to a giant company who makes their money, wait for it, selling ads!
Do you also not think that they're listening to what TV shows you're watching, keywords in coversations, etc? It IS always listening btw - it has to in order to pick up on keywords such has OK Google to activate it.