One of the great things about capitalism is that it has some redundancy and resiliency. Competition may also lead to new features (markets), etc. On the other hand, this is duplicative and wasteful. Contrast the duplication (redundancy) of the capitalist system to the one producer model of communism. Less duplication but less resiliency and less ability to find new features (market). I think when a market is young and returns are high that it makes sense for many producers. However as a market matures, we can shed some of the duplication and allocate it to other new markets. If the monopolist restricts quantity sold? Easy, it increases the tears for a new entrant. The system manages itself in this way (in reality no system at all, it's decentralized coordination).