I thought this was obvious. Why else would they be worth so much unless they were more efficient than traditionally structured firms. Silicon Valley got rich through automation of previously manual processes. Automation is about removing people from previously man-hour heavy processes. Less man hours equals less jobs. Productivity is now almost totally decoupled from man hours. It's not rocket science.
We stand on the shoulders of giants. Everything is a iteration of something old. Sometimes a pretty big one, which we call innovation. That's not to say that they aren't on an order of magnitude better and more efficient than previously but that's exactly the point. We do way more with way less these days. I do believe new industries will emerge from the ashes of old ones but there will inevitably be a transition period where things will not work very well for those not working on the cutting edge of tech.
