I think it is easier to be polite always and not switch between polite and non-polite mode depending on who you are talking to.

To machine. It just easier to be polite by default than split our language into two forms "I speak to human" and "I speak to machine". Because the chat interface is really close to what we see when we speak to human. Well, exactly the same.

Anything or anyone. Being polite to your surroundings reflects in your surroundings.