They still go off model fairly frequently though, they just don't go as far with it
I hate that 4chan doesn't understand and in some cases is outright opposed to the idea of moderation, because good cartooning is based pretty much entirely in it.
If your characters are always on model, you get shit like family guy, where it looks stiff and lifeless and bland. Meanwhile, if you throw out model sheets entirely you end up with shit like OK KO, where it's distractingly inconsistent.
Animation only works when it hits a balance that allows it to be expressive while also being consistent.