That's a fairly standard automated PCB assembly line. I can tell you with 99% certainty that Foxconn workers aren't placing surface mount parts by hand. Machines that can do it are relatively inexpensive (On the order of $1 million) and work many times faster than humans (and many times faster than the machines in that video) with near-perfect accuracy. They will also work 24/7 without creating controversy in western media.
What human workers at Foxconn are doing is final assembly work, such as putting the device together, and maybe packaging it. Robots to do that would be more complicated because a lot of dexterity may be required, and programming them for new products may be difficult because of the wide range of possible movements. For a SMT pick-and-place machine, programming is as easy as giving the machine some design files that tells it where to put the parts, and the basic movements are the same every time. To make a robot that places an assembled board into an enclosure, for example, is more difficult because the enclosure could have any number of shapes.
Here's an example of a modern pick-and-place machine:
Even with a virtually unlimited number of workers, there's no way you could match the output of even one of those machines. Humans make mistakes, so the yield would never be good, and it is extremely difficult for humans to place parts with the fine precision required for ICs with a high pin density.