Status anxiety pushes people in AAA studios. And at the top, there are collateral opportunities that add even more (perhaps misplaced) status -- like the way Bioware writers used to be able to parlay that into novel writing jobs.
Basically any time someone learns I work on games, there is an exchange that goes, "Oh! Anything I would've heard of?" And they've heard of none of it, except maybe Dragon Age. If I'd said, say, Gears of War or Uncharted or Assassin's Creed, they would've heard of it. That desire, the sense that people outside the cone of nerdom care about what you spend your life doing, is a powerful motivator for people. When you can parlay it into something even more comprehensible (like, say, working on a novel -- even a fantasy novel -- or a TV show -- even some crappy foreign-made cartoon), there's yet more status to be had. At the end of the day, most people will suffer bottomless indignity within their workplace to feel dignified for the couple hours of waking free time they have outside of their workplace. If that wasn't so, people would make all sorts of different professional choices.
Another major factor is that people imagine that their work will be better with a bigger budget behind it, and there's some truth to that. For example, I'm sure Primordia's writing would've sounded better voiced by Clinton Eastwood and Jonah Hill or whatever, and the scenes would've had more pathos with Pixar-level 3D animation or whatever. I guess. And you can basically fit that allure into any discipline ("my art would look better backed up by a team," "my music would sound better performed by an orchestra," etc.). Maybe not coding, but game coders are weird, no really good coders go into gaming* AFAIK unless they are passionately obsessed with games, and that obsession is probably going to lead you to a franchise you enjoyed as a player, not to an indie project.
(* A good argument could be made that the same is true for writers, artists, composers, etc.)
So I'm not surprised that people wind up at big studios, that big studios wind up making ever-more-Hollywoodish projects, or that this process is dehumanizing. But at the end of it, would anyone at all care what Amy Hennig had to say if she hadn't worked on these AAA titles? It would be like a Jeff Vogel soapbox thread rather than Breaking News: Video Game Designer Speaks!