Consolidation leads to efficiency. Which in the case of commodities, is the only way to ensure low prices. A new slaughter company is not going to innovate a more efficient means of producing a pound of beef. In theory, a perfectly run state monopoly would be the ideal system. But that rarely ends well. In the US we've worked out a sort of half way between the two extremes, where large private corporations are allowed to consolidate in the name of consumer prices, while still maintaining just enough competition for profit motive to keep things well run. It's not perfect but it's the best we've figured out so far.