Because there's still ape habitat that people don't want.
And incidentally, humans didn't evolve from apes: humans, apes, chimps, gibbons and gorillas all evolved from some common ancestor who, like the mammoth and eohippus, is no longer with us.
And we know that the habitat of the 'common ancestor' no longer exists because the 'common ancestor' no longer exists. Just like the mammoth habitat no longer exists because the mammoth no longer exists and the eohippus habitat no longer exists because the eohippus no longer exists. But the coelacanth habitat still exists because the coelacanth still exists.
Evolution is really easy that way. So easy that a cave-man can do it...