Supply and demand; the supply of people who want to be writers is too high, and you are going to have to go to
great lengths to distinguish yourself or get
really lucky. As others point out this may not be the only way in, but don't expect anything to be easy or even merely hard, because every metaphorical door into the place is jammed tight with people trying to get in.
We get the same effect in our industry with games programming. Nothing about games really especially calls for endless deathmarches or 18 hour days with no overtime pay six days a week, any more than any of the many other industries in which programming is as critical or perhaps even more critical (there's more to games than programming) but somehow manages to get done in 40-ish hours a week. It's just the endless hordes of young programmers who think it's what they want to do driving the price through the floor by inflating supply until there's just no incentive for EA to treat them any better; they're not just replaceable, they're aggressively replaceable.
I really recommend against any of these careers, the risk/reward just isn't there. The risk is much higher and it turns out there are many, many other jobs out there that are just as rewarding, except without the possibility of fame for a small percentage of jobholders.