The fact that economies of scale exist means that even unregulated markets will consolidate. Regulation is an orthogonal concept. On the spectrum of market competitiveness, one extreme end (perfect competition) is an unstable state, and the other extreme end (monopoly) is a stable state. As consumers we benefit from competition, but free markets abhor competition. Something needs to intervene to reintroduce competitiveness into monopolized markets, and that something is going to be indistinguishable from a government.
I agree that even less regulated industries have monopolies, you're right, but those will tend to be companies that either have a natural monopoly (e.g. they own some land) or are so competitively priced enough for their customers that there's no obvious way to create a competitor that can take market share from them. I don't see either of those situations being improved by constant government interference.
