Oracle Database Discussions

Hi
I am working on a project where I see that in most of the tables composite primary keys are maintained. My question is isnt it easier to have a single primary key in place of multiple - When it comes to querying those tables, maintaining etc? I am trying to understand the model by querying different tables but am realizing that these multiple PK are just making it difficult to understand the actual purpose, relationship etc.

What would you suggest? I am still in the early stages and things can be changed. i am worried about getting unexpected surprizes when I move to Qa environment.
Any insights greatly appreciated.
Thx!