It's simple really....first an allegory though: why aren't tigers evolving into super-genius tigers?
it's the same answer youre looking for. i'll explain:
Tigers aren't getting much smarter because theyve become smart enough to succeed well in their environment as-is.
monkey's and apes are NOT our direct ancestors...they are our ancestral cousins. SO....for monkeys and/or apes to start getting really intelligent & self-aware, they would have to be exposed to similar environmental stresses that OUR direct ancestors were....in our case, it was a massive volcanic eruption in the area of Turkey...the ash and fallout combined with the exact location of our ancestors at the time, and the localized environmental difficulties (sparcity of food and water?), pressed us to the absolute brink of extinction.....
We were already quite smart...and social (teamwork emphasises intelligence as well). So, the pressure put even THAT much more emphasis on our #1 trait (intellect, problem solving & teamwork).
As a direct result of this scenario....two things occurred:
1. we were nearly wiped out (modern estimates suggest we may have dwindled to 3,000 individuals)
2. the few who did survive...barely managed to do so...and only due to some rather clever thinking, tool manipulation, and cooperation.
This pressure of this, "Figue-it-out-how-to-survive-or-perish" scenario, thrust us forward in intellectual development so far that our intellect became SO important to us, that it soon became the only key defining feature in our species' evolutionary focus. So success in our social groups became pretty much one-dimensional....either be smart and inventive or stay at the bottom of the totem pole and fail to mate as frequently...or fail to survive at all.
hope this helps...