Because most of the bits are not about how funny slurs are, but about how stupid, pointless and dumb life is, how most of it is incredibly arbitrary and random, and how much comedians, including themselves, have always sucked as people. Like the running joke on the podcast was that Adam, who is probably the nicest person on the pod, is also the least funny.

The funniness of slurs mostly comes from disscissions from the arbitrary and pointless nature of most language. None of these guys particularly like using slurs in anger, but as a punchline, with one of the longest running jokes being that they will end the pod after Nick says the N-word (which they never actually did).