Pain is supposed to tell us, fire bad, no touch fire, things like that. But unfortunately, we all know there are those out there who are wired differently and actually like pain, and there are those who like to cause pain.
I think developing a way to enable the sensory response in robotic constructs may be a step or two away from self-awareness and then the rise of the machines.
Robots/Androids/AI will very quickly realize that the vast majority of humanity is utterly useless and will likely try to create a clean slate.
That is what most people fear. Me too actually.