Siri is a great assistant to help you use your phone. But the audio greetings, whether intentional or accidental can become undesirable since they aren't muted even when your phone is muted. However, you can mute Siri by following some simple steps.
Everyone has people in their contacts that they only know by relationship. Whether the relationship is professional or personal, it's often hard to remember names and phone numbers. Apple has given Siri a way to learn about those relationships to make your life easier.