This was a question that I pondered as well. Some of the things people have made recently just seem really creepy how human like they are, however, this video answers this question.
Basically we have already designed a world made for humans so to have a humanoid robot would make sense to be able to navigate our already human designed world.
Now, some of the robots with human like facial features may still creep me out at the moment, but I can see where having a human like thing to interact with can still be important too.