First of all we didn't evolve from apes. We and the apes evolved from a common ancestor. Which was probably very much like an ape.
Secondly, apes are still evolving! Given time, millions of years, they might evolve into more intelligent beings! Some people used to think black people in Africa were evolving apes, but not as far evolved as us. (No kidding! They really did! This was a justification for slavery.)
Some species have been around for tens of millions of years without changing at all. Alligators and crocodiles, for instance, have been just the same since the time of the dinosaurs. So why didn't they evolve? There is a part of evolutionary theory called 'punctuated equilibrium' that explains why part of a population evolves and part doesn't.
The way it works (according to the theory) is that a population of animals evolves to match their environment. Once they do, they stop changing because they are 'perfectly' evolved for their environment. Then some group of these animals leave that environment--for instance, the valley where they live is crowded so they migrate over the hills into the next valley. The environment there is different, so those few of those animals who are better suited to the new environment have an advantage, so they they begin evolving again until they once more reach 'equilibrium' with their new environment. So now you have two species, or subspecies, where before you had only one.
In fact this was what led Darwin to this theory in the first place. He visited the Galapagos Islands where each island had a slightly different variety of turtles, birds, etc., because the environments of these islands were all a little different.
Meanwhile those crocodiles, who have been in equilibrium with their environment for all this time, haven't changed much in 40 million years, because their environment hasn't changed!