Why does sudden impact not have a adaptive damage aspect to it?

I'm not trying to get this rune nerfed since assassins are primary users of this but does this rune not have a adaptive factor into it unlike a lot of the other runes.

I bring this up because Katarina seems to keep getting nerfed and I feel the non adaptive factor of this rune is probably playing a huge role in this because her mix damage allowing her to take advantage of both the magic pen and lethality bonus unlike most assassins who specialize in one type.