I play with friends now and then but NPC's are available and do what I want when I want and can fulfill their role without needing to be entertained.Why not wing up with some real people?
Also if done lime in the DDF they would each have their own back stories with possible missions attached to them. There would also be RPG elements with different quality of NPC with training etc for some long term play.
I get many players prefer playing with real people. I guess I am a bit of a dinosaur in that for me MP with friends is the icing on the cake, MP with randoms holds no interest to me at all, and single player gaming with NPC's is the cake