In his inaugural address, President Obama said that "The question we ask today is not whether our government is too big or too small, but whether it works." This is a commonly heard argument in response to concerns about the growth of government. Who could possibly be against government when it "works"? Why not instead consider each proposed expansion of the state on a case by case basis, supporting those that "work" and opposing any that don't?
Taken seriously, this argument leads to the rejection of any systematic constraints on government power. Why should we have a general presumption against government regulation of speech or religion? Why not instead support censorship when it "works" by improving the marketplace of ideas, and oppose it when it doesn't? Think of all the misleading speech and religious charlatans that government regulation could potentially save us from! The answer, of course, is that government regulation of speech and religion has systematic dangers that are not unique to any one particular regulation. Given those systematic flaws, it makes sense to have a general presumption against it.
The same holds true for government intervention more generally, including in the economy. It too has systematic flaws that justify a presumption against it.