Because thank God, there are somethings NO ONE wants to develop. How would you sell that to a development team? "Hey guys, great idea for a game - let's make it based on those poorly written books and equally badly acted movies: Twilight!" I'm sure all the people in the building will be screaming like little girls...not.
Seriously the only way you could make a Twilight game is to get a bunch of damn women to make it 'cause they're the only ones who want one. If you had a team of women developers making a Twilight game...we'd have Twilight Forever - they'd be sitting around watching those damn movies at work all day and getting off watching that douchebag sparkle. Vapourware in the making!!
Thankfully my brain cells have been spared, as I know people who have read the book and have watched the movies...and from that collective information I know it's utter shit. Bunch of damn zombies! I believe some here might take enjoyment from this (I know I sure lol'd):
http://www.youtube.com/watch?v=MQCFlXzKbM8