One has to wonder if it produces better responses (or worse ones).
Manners cost nothing.
I assume you must be joking, but for the avoidance of doubt - I'll just say that I don't consider it ill-mannered of me not to thank my vacuum cleaner when I've finished using it either!
Just because we interact with a machine with a familiar human language doesn't mean the 'social' norms for that interaction are or should be the same.