Even if "you don't have a problem with 30fps" that doesn't change the fact that 30fps is an objective downgrade from its predecessors.
There is no 30fps game that would suffer for being 60fps instead.
But there are games at 30fps that would benefit by being 60fps instead.
From the minimal research I've done, it was stated that since "the environment itself will be moving quickly, and without warning" and that with so much moving on the screen at once, 60fps would cause undesirable slowdowns.
I came here to chew bubblegum and kick ass, and I'm all out of bubblegum. http://d24w6bsrhbeh9d.cloudfront.net/photo/5062421_700b.jpg