The ones that I know have a function are:
*Tutorial class (people can talk to them to learn about the game)
*Rifleman (can join your squad to attack creatures) some NPCs might also do this, but I'm not sure
*Dirt haulers (mining)
*Builder (constructing facilities and stations)
*Worker (constructing ships/vehicles/items)
Light speed is too slow! We're going to have to go right to...Ludicrous speed.
Amp Thane, Captain, BFF-1 class freighter EQUUS