When you are pleasant and acknowledge with a "good morning", "How are you doing?", or "Good job!" — you let people who are working in your company, regardless of their status and role, know that you SEE them, and are not too important to say a pleasant greeting. Then you have an ally who doesn't feel you are too important to be civil. And, when you need something they are more inclined to assist you, because you are not too important to be a colleague.