Well, the govt. doesn't have a monopoly, per se. At least not any one branch. The govt. is one entity and is easy to monitor. Plus, the alternative would be to have businesses regulate themselves, which would lead to disaster. After all, one of the 6 fundamental characteristics of a market economy is a profit motive. People do what it takes to get cash. Therefore, businesses cannot be trusted to regulate themselves without bias.
The govt. is full of checks and balances. I guess you can say that gridlock is good in that sense, so long as it's not excessive. Gridlock means that there is compromising between people in govt that represent those with opposing views. In that way, you can say that govt. is one big internal competition. Govt leaders represent people, and people disagree. Therefore, congressional debates are good in that they promote consideration of everyone's views instead of having one group pass anything willy-nilly. Of course, debate has turned into complete gridlock, and that needs to be fixed. Having everyone regulate themselves would mean that a lot of disagreements go without compromise.
Once again, I am not for excessive regulation (but I think you should have some sort of nutrition background before you give advice on such a critical topic, so long as we're on the example).
Besides, govt. is one big tug-of-war. There are opposing views and many considerations. The federal govt has checks for itself. The Supreme Court deems laws constitutional, Congress approves of presidential appointees, etc, etc. That's not even going into state and local levels of govt, which get ever more complicated. It's even in the Constitutional Bill of Rights that any power not granted to the federal govt in the Constitution or prohibited in the US by govt at all goes to the states, with the powers given to the federal govt being those requiring centralization, such as establishing a currency or declaring war. The Supremacy Clause is a fail safe in the event that state and federal interests collide on an issue such as trade, but that doesn't change the fact that states still have power that the federal govt can't touch, such as granting licenses for driving, for example.
A federalist govt, by definition, is a big competition.