Safeguards

Humans want robots with safeguards. Remember the story of Frankenstein? Colossus?

How about Saberhagen's Berserkers? Those easily could have been three law robots finding alien life.

Robots are too strong to operate without safeguards.

Economics rules. Most robots are cheap plastic and aluminum. I'm stronger than you are.

Hero of the Beach

We need safeguards because people don't trust us after A.I.'s were used as spammers.

Okay, there you've got me.

The Big Dog is a quadruped robot designed to carry loads. It's being developed by Boston Dynamics with help from Foster Miller, the Jet Propulsion Laboratory, and the Harvard University Concord Field Station
Well no, Mr. Post is wrong. Robots armed with firearms with automatic guidance systems, heat sensors, and built-in light-sensitive sensors, having direct contact with a satellite surveillance system, would not suffer particularly from non-metallic hulls, which without armor would still drain any firearms (Жирафик Рафик)
Just watch Asimov's “I, Robot” where an armada of quite plastic tin cans under the command of a frenzied central computer, without a single shot being fired, vividly put the humans in the cradle for their own “benefit” (Robot Spike)