No pain, no empathy. It's our best shot of AI not taking over after technological singularity, IMO.

Also, I think androids will be pit against each other for human amusement. Pain receptors would make this unethical. This is important, I think, because cheering on violence hold us back; keeps us from progressing toward love & unity.

Ultimately I think the answer is, most AI should be able to "feel pain" and most robots should at a minimum have damage-avoidance sensors, but perhaps not all.