The purpose of fast zombies is to hunt down and kill runners and people who are in spots other zombie cannot reach. If this is executed correctly is another conversation. I am not exactly familiar why Infected have completely replaced Normal Zombies neither. For those that don't know, Infected A.K.A Fresh Dead as they are originally known are supposed to be what humans get transformed into when they get killed. They are basically a downgraded normal zombie but with the victims player model and are supposed to be in the middle of the stage of human and zombie. Why this has been available as a zombie class to choose I have no idea. Im not too sure I agree or disagree about this decision. My only problem with them is the ugly view model they have. The whole zombie roster is strange and messed up for the worse in my opinion and the quality of most of the mod is not helping the situation. I just wanted to clarify some stuff and nothing else.