While it doesn't take much to elicit a social response, people are accustomed to high quality output. Any well-designed interface requires on providing good, appropriate, and timely feedback. Similarly, a conversational interface, enhanced with recognizable facial features, arouse interaction and expectations. Delegation and speech interface are not always the best way to complete a task. Provide users with options to interact as they prefer.
Software often breaks simple rules of etiquette.
In any social context, humans expect reciprocity of politeness. All of us respond to praise, even when it isn't warranted. Adapt to the user's personality type and work style. We work more effectively with others when we feel we are matched as a team. Treat the user as a teammate.