Different habitats lead to different selective pressures.
If the last common ancestor of apes and humans was 4 million years ago, why haven't apes lost all their body hair and developed the ability to run on hind legs?
Because they don't live on the open Savannah, of course.
Speech & advanced tool making is more complicated, but we can surmise similar ideas apply.
For example, maybe human pack endurance hunting in the Savannah increased the value of social structure and sophisticated communication.
If the last common ancestor of apes and humans was 4 million years ago, why haven't apes lost all their body hair and developed the ability to run on hind legs?
Because they don't live on the open Savannah, of course.
Speech & advanced tool making is more complicated, but we can surmise similar ideas apply.
For example, maybe human pack endurance hunting in the Savannah increased the value of social structure and sophisticated communication.
FWIW, apes do use simple tools.