Many of these companies aspire to things that are great for themselves, like controlling markets and integrating vertically, but not so great for everyone else.
https://www.uber.com/jobs/list
(of course the sector of businesses we are talking about isn't very well defined)
Besides these "do it for me" markets, roughly the same pattern is seen with app-stores, and probably many more markets.
(Of course, in a truly free market it should in theory be possible to create such nested markets, but this just shows that the concept of a totally free market is nonsense, and that we should act against these patterns.)