Personally I can't stand NPCs who are members of The Party. The Party is a sacred organization that should only ever include PCs.
Now, long term NPCs whom The Party interacts with on a regular basis is a different thing. If The Party travels the galaxy in a Corellian Corvette, then the crew that runs the ship will surely be interacted with on a regular basis. Some NPC crew members might even have names, and The Party might even be sad if they die. However, during the tense negotiation in Jabba's Palace wherein The Party must once again explain to Jabba that they can't pay off their depts, Random Crew Member #32 will not be present, even Captain Hat With A Brim won't be there. Only the PCs will be because they are the stars of Corvette Shenanigans: A Star Wars Story, Captain Hat is just an extra.
The PCs are the movie stars, the NPCs are the extras.