I'm not trying to say that the game objectives have any real meaning to them, but how are the social aspects not meaningful? You talk to real live people through chat and voice, in real time. You make friends, just like people do here on RAFO's message boards. Your friends go off to do something together, and you say that you'll help them out. If you quit once things have started (particularly if you're a main tank like LL, or play some other important role) you've likely ruined the activity for your group of friends as well. If you ask me, that means you have a social obligation to continue once you've committed, as long as nothing more important than helping your friends have fun happens to come up.

Do you not agree? Maybe a bad analogy would help? What if your real-life friends planned a camping trip, and you said you'd drive because you're the only one with a truck? Everyone packs, loads your truck. . .then you tell them all to get out, because you don't feel like going camping anymore. Maybe they can call around and find another ride, but that's a hassle, and even so they may not find someone else with a truck. Now, your friends would obviously understand if something came up at work last minute, or a family member got sick, whatever. But just to bail because you decide you don't want to anymore?

Anyway, I'm sure you feel that the importance of video games is negligible compared to anything happening in real life, but that's not the point. Your social obligation is to the friends you know and like, not to the game itself.