Me too, except that in my case it's the opposite. I thank my car when it's running well, and so on. So for me, being nice to the chatbot and thanking it is already natural. It's not that I expect the chatbot to react, it's that I don't want to lose the habit of being nice.
I think there's actually much here tbh. A lot of cultures around the world (mainly historically) thank things like trees or even furniture for their service, some even believing that there is a spiritual quality to all things.
I don't believe any of that, but I do think that a general attitude of gratitude can be very beneficial to one's happiness and general outlook. IMHO psychologically your approach has benefits.
