Sometimes one is able assist another person immeasurably even though that act of kindness was insignificant in itself. It might not have saved a life or been as dramatic as the rescue of an animal in distress, but that act of kindness could mean more than life itself to that recipient.
In this case it was a New York Taxi Driver who as an occupation is not normally known for their patience and tolerance. This incident probably meant more to this doddering old woman than anything else in the past ten years of her life.