Because not all apes evolved.
Just because you make apple pie doesn't mean there are no more apples.
Well, not quite. Our primate ancestors all evolved, just into different things. Some evolved into humans, others into chimps, bonobos and gorillas. It is wrong to say that a population hasn't evolved -- all are continuously evolving -- just as its wrong to say that apes are any less evolved than we are, because evolution doesn't have a direction, and the real test is whether an organism is fit in the context of its environment.