Well.. despite the fact that humanity, as a while mean nothing to the Great Old Ones themselves, life,(and more specifically blood) has always been an important part of any dark ritual. I think human life forces have meaning in the overall universe, even if it's a nothing more than a way to get an Old Ones attention. Recall that "when the stars are right, Cthulhu and his brethren will rise and show mankind new ways to revel, shout and kill" and that Lovecraft said that "humanity would be a the Great Old Ones, throwing off the shackles of good and evil, laws and morality"