"Using a person's name is a key to opening doors for you and to maintaining an initial rapport that could turn this person into a new friend for life or a lifelong business partner."
"In particular, when we hear our name, we don't simply attend, we jump, alerted, aroused, vigilant. Even if three names are recited at a time, we hear our own (but only our own) quite clearly."
When someone uses our name we remember them more readily. The same goes for NPCs who use the name of your character. If you want the players to remember an NPC, have that NPC use the character's name when talking to them.