As players' time in the game wears on, they see more and more violent events. Many quests ask players to kill NPC animals or people. Art props in the game world often include bones and corpses, and less commonly, wounded NPCs.
My suspicion is that after a while, some players become inured to the violence around them, and become less likely to respond to pleas for help from the NPCs. At the same time, players learn more about how the game works, and discover how to direct their play experience towards the improvement of their characters. Some players become more likely to pick up a quest for its XP, gold, or gear than for the emotional reward of assisting the NPC.
If the joy of altruism could be maintained throughout a player's in-game career, it ought to provide for a more engaging experience. Briefly, here are a couple of methods that may help with this goal -
- Let the player see that they've changed the world around them for the better. Admittedly, this is easier to do, and more commonly found, in single-player games than in MMOs - but even a wave and a smile from an NPC can help them seem more human and less like XP vendors.
- Tell the story in a way that players understand. If a quest is too wordy, it won't get read, and if the story is too complicated, players will ignore it. Many games succeed by relaying the narrative with the help of the world itself.