"Going up?" "Yes, thank you." in an elevator.
In a certain movie, a man was waiting for an elevator. The doors opened and there was another man standing in the elevator. He asked "Going up?" to the man as he entered in. Then, the another man said "Yes, thank you."
I don't see why this man in the elevator answered "thank you" to the man who asks "Going up?" Is this natural to you? He just wondered whether this elevator was going up or down, right? Asking those questions in an elevator is supposed to be grateful for?