It's not even THAT simple.
For instance - you would think that putting a bolt in a hole and running it down would be a perfect task for a robot.
But it's actually kind of a bitch. Feeding the bolt correct, in the right orientation, and verifying you have the RIGHT bolt is just the first step. Making sure the socket engages, that you don't crossthread, and that you don't push so hard you roll the leading thread over so it can't run down is just another. The next is verifying you got the bolt all the way down. You can monitor torque - but what if the whole isn't threaded to full depth? You can monitor rotations... but what if the top threads are too loose so they don't trigger a torque threshold to start counting? What if there is moisture in the hole from a washer process that causes backpressure so you get premature torque readings? What if the threads on the bolts are damaged?
I could literally go on ALL day about how hard these tasks really are. Making hamburgers with a robotic system isn't easy. And I guarantee that when your automatic burger baking system fucks up, all those customers waiting in your drive through line are going to be mighty peeved.