It's to encourage a bit more thinking before you shoot, and make zerging less effective, and also to allow panic to be used as a weapon. It's nice to have a bit of psychology in a game, and games like Dystopia have funky little features where they short out most of your heads up display under certain situations, basically meaning that you're fighting blind. Those times, when your vision is filled with EMP noise, and when there's an invisible man running around your allies, they wouldn't work unless FF was on forcing you to think rationally through all this.
Of course, a lot of games work better without FF, but there are situations where it's an absolute godsend.