Some instances and raids, you understand why you're there. Icecrown, for instance, makes a lot of sense to me. I get why we're running the five mans (trying to sneak into the Citadel while the Scourge is focused on the front door) and the raid (that didn't work out so hot so brute force it is!) I always enjoyed Scarlet Monastery and had no difficulty with why I was running the place either as Alliance or Horde. Alliance, you were cleaning out a nasty pack of gibbering mouth-breather sociopathic xenophobes who were totally freaking insane, and Horde... same deal, plus they were killing people you actually knew.
But I always had a terrible time understanding why I was running Maraudon. Okay, there's some centaurs, and they're... bad? I guess? And then there's one of Cenarius' two sons buried here, and he and an earth elemental named Princess Theadras had sex which, okay, I guess that's bad? And we're going to kill her for having centaur babies with him, and... there's a pretty decent set of plate legs in there? The instance itself isn't poorly designed, mind you, and there's a nice lore element when you bring Zaetar's seed to his brother Remulos in Moonglade, but in terms of why your characters run Maraudon at all, well, it's really hard to come up with anything like a compelling reason. Unless you're a tauren, I guess. Tauren don't need a reason to kill a bunch of centaurs. They just need to be told where they are.
This is always my biggest problem with Zangarmarsh and Coilfang: why are the naga stealing all the water? Just to have it? How does this benefit Vashj or Illidan? I don't really understand that part of the plan. I'm sure someone, somewhere explains it, but I guess I missed that part. (Dread Lord Ziebart hastens to mention that she does have a throwaway line basically saying 'Dudes need water, so we're gonna have all the water and then y'all will have to do what we say' but it conveniently ignores places like Nagrand and Terrokar.)
So now I turn to you, Breakfast Topic readers. What instance or quest most made you say "huh, why is this even happening" and why?