Because the social issues happen at a more biological level, hormones and cell signaling and stuff. Robots are at a much higher level. Online girlfriends are cool, but as we all know, not a replacement for physical touch, intimacy, and relationship building. Your body doesn’t release oxytocin from cuddling with your cold computer.

Maybe we can eventually “trick” the human brain, but I think it will be much more challenging than people think. I would imagine if people even just knew someone was a robot, the jig is up. For most people. It wouldn’t be enough to create the perfect humanoid robot. We’d also have to make them hidden in plain sight. Full Ex Machina style.

Did you really mean to write really: "Online girlfriends are cool"

In my humble opinion, they are the epitome of uncool.