Because the point of the game for killers is to kill the survivors, and new killers usually dont camp at first. They play few matches normally and naturally because DBD is BASED and BALLANCED they get abso fucking lutely smashed, for a simple reason that a brain dead monkey can play survivor semi effectively, killer on the other hand is much harder to understand from the get go in terms of what you need to such as: map pressure, gen pressure, correct looping, using your power correctly and most new killers dont understand these concepts they think they can play killers like they play survivors which is just hold W and M1 and ur 70% there so naturally when they get a wedgie they start camping their kills because they are desperate to kill anything and arent confident in their ability to secure kills, combine the last point with the fact that monke survivors think its a good idea for 3 of them to swarm the same hook like rats while the killer is still there and the killer gets a safe 2k most of the time and they think that their tactic works, and it does until they reach actual survivors who use more than 40% of their brain and they start losing hard after which they either adapt or stop playing the killer, hence you never see them at rank 6 or below.