I was never sure why they made the NWN1 and NWN2 player centric. I always figured that the very early computer RPG's like Akalabeth, Wizardry, Ultima, Bard's Tale, and Dungeon Master preceded LANs, and since what they simulated was multi-player tabletop RPGs like D&D, they allowed the player to create and control a party, allowing the player to experience multiple character races and classes. The post-LAN RPG's like Baldur's Gate and Icewind Dale were intended to be played over the LAN like Doom, with each person controlling a single party member. But because not everyone had access to the internet at the time, the developers also created NPC's to act as party members as well and also allowed the player to create multiple party members, as had the earlier computer RPG's. By the time NWN came out the developers had decided that almost everyone should have access to the internet and so they should design the game assuming that people will play over the net with other people and there is no need to allow people to create and control a party of individuals anymore. Technology had removed the need for simulating playing with friends by allowing party creation. What they didn't consider is that some people like creating a party and may not want to play with friends over the net. You'd think that a bunch of developers who were likely introverts wouldn't have made that mistake. Thankfully they fixed that for NWN2 with the features released with SoZ.
Regards