Do Androids Dream Of Electric Sheep?

The first four chapters of  Do Androids Dream of Electric Sheep? gave us a main character with the name of Rick Deckard who is a bounty hunter of androids. Rick is on search of nexus 6 androids that look exactly like humans and do not want there cover blown. I do not understand why these androids where built to look exactly like humans. If it is a possibility for us to create those androids in the first place, I don't see why they could not have been built to look more like robots. Besides that fact it is interesting to see the kind of mind warping advertisement that is shouting from the TV sets. The steady progress of advertisement today definitely seems to play along with the books portrayal of ads in a apocalyptic era.