Indeed, a lot of businesses with economies of scale and network effects can become monopolies. If we want to experience the benefits of free-market and competition, from a consumer point of view, we need to implement it through regulations. Peter Thiel explains it quite well, businesses want monopolies because they can reap a higher share of the value. Competition redistributes value to the customers. Once we recognize this, we can ask where, as a society, it makes sense to foster competition.