My own, rather limited, experience is that because of the huge number of people who (1) are fans of games and (2) think they can write/design games and (3) therefore apply for these jobs, the easiest thing for a company to do is not hire someone with no experience. That is compounded by the fact that game writing
is a different art form, and it's very easy to do it wrong. When I was applying (successfully) to Bioware, I'm fairly sure they only looked at me because of my experience with TimeGate and the oddity that I was a law school student. They liked my initial prose writing sample, but I then flunked the initial dialogue writing test. For whatever benevolent reason, they gave me guidance and another try, and I passed that time. (If anyone is curious, I guess I can post portions of the samples I did.) When I failed the test, that was after having spent years writing fantasy (including for games, even including some branching dialogue) and at the peak of my cRPG-playing days. Even still, I screwed up fairly basic stuff because writing branching dialogue is so different from anything else.
This is why I think there's a considerable amount of luck (or unknowable complexity) in the process. There was a cascade effect from my original paid game writing job that led to my having the credentials necessary to get a look, coupled with the entirely unpredictable benefit of being in law school. And there was the good fortune of them giving me a second chance on the writing test, and the double good fortune of them giving me guidance that allowed me to pass the second time.
I am quite confident that
MicoSelva or
Darth Roxor are more than talented enough to be writers; but without other variables coming into the right constellation, it can be hard for things to work out.
Incidentally, I haven't played D:OS, but I do think that sometimes bad stories (and even apparently bad writing) happen despite good writers -- sometimes you make a bad judgment early on that locks you into a story turns out not to really work, sometimes design constraints prevent a solid execution of the story, sometimes bad VO or bad translation obscures good writing, sometimes the press of deadlines requires settling for less than your best.