content: Basically this. Notice that each new industry that people move to requires more training and higher skill levels? Humans each have inherent skill caps which limit how far they can climb this slope. Most peoples' skill caps are above the level where simple mechanization or automation can replace them. Most peoples' skill caps are below the level that even today's AI technology can reach. Give it 20 years and the only unskilled jobs left are going to be laundry, entertainment and prostitution (which is entertainment, I guess).