Whenever I ask Siri a question and it provides a generally helpful answer, I always say THANK YOU. I have absolutely no idea why, and even though I’m aware how dumb it is, I can’t seem to stop. Such a weird habit.
Does anyone else regularly thank their virtual assistant? 
Not exactly the same thing, but there’s a UK grandmother who uses “please” and “thank you” when typing requests to Google (e.g., “please translate these roman numerals MCMXCVIII thank you”).
That little quirk just might save you come the inevitable Robot Uprising.
That’s why I do it. 
But also, I just think it’s good for one’s mental health and well-being. And if you get out of the habit of thanking others, it’s easy to forget to do this in other parts of your life.
It’s possible that those of us who grew up with the movie, "2001: A Space Odyssey* feel a particular compulsion to treat these virtual assistants with more than a modicum of respect.
And I do agree with @robby that it’s just a good habit.
I do exactly the same thing as the OP. Thanks, Siri.
Is it possible that Siri pays attention, and when someone says Thank You, the AI logs that as an indication that the answer was a good one?
I read an article a while back that mentioned the need to do this if you have young kids. They don’t know that Siri and Google and Alexa aren’t real people. If you want to model common courtesy, you have to include them.
I happen to also think that it’s a habit you have to keep up, and that if something registers to you as human-like, enough that you automatically give it courtesies, it would be harmful to your own humanity to try to train yourself out of it.
What about all those automated telephone menus and things like calling your bank to hear a list of your recent transaction, e.g.?
For a long time I always listened to the end of those before hanging up because I’ve been so programmed to not just hang up on someone in the middle of what they’re saying.
But now, I just hang up as soon as I’ve heard whatever I want to hear.
I like this thought. However, my parents have named their roomba “Little Bastard”. Fortunately they don’t talk to him directly, just behind his back. (Yes, it is a he.)
I’ve never felt compelled to say please or thank you to those, – they’ve never registered as real people – and I broke the habit of not wanting to hang up on even real people when telemarketers would keep talking even after I would say, “thanks, I’m not interested.” So I don’t count that example, myself.
It’s possible they could add a function like that, but I’ve never heard that they have and you would think Apple would want people to know they could be improving Siri in such a way. But it really doesn’t sound like it would be a particularly good way to improve the quality of the answers.
Yeah, I’m not polite to my Siri, and now whenever I ask it a question it says “I’m sorry solost, I’m afraid I can’t answer that”.
I really like Siri, she’s always eager to help. Of course I thank her!
I once asked Siri if she loved me. She replied, “Oh, look!! A puppy!”
If you really wanted to mitigate risk, I would probably curtail any extravehicular activity for the foreseeable future.
– “I, Mudd” by Stephen Kandel and David Gerrold Star Trek TOS Season 2, Episode 8 Nov. 3, 1967