Because people are choosing government to control markets and their lives. When your life is far more free and you are far better off with a free market. Got it now?
Don't be naive, there's never going to be a truely free market, even if you somehow got all the governments of the world to pull out (remeber, it's a global economy now), the corporations themselves would destroy it very quickly, they have nothing to gain from a free market, no, the money's not in healthy competition, quite the opposite..
You know why there doesen't exist a truely free and self-regulating market? it's because it doesen't work, it's a pipedream to rival Communism, and the Government constantly had to step in to prevent abuse, because the private sector has zero personal interest in a free market, it's not good for buisness, it keeps prices down instead of up, ohh no, it's no good at all, it's so much easier to just engage in price fixing, and so much more profitable too!
Now you're a man with a hardon for the constitution, yeah? then you must also realize that the real ingenious part of that piece of parchment is the checks and balances that are written into it, without thouse, it would all be worthless, it could all be easilly taken away, makes sense right?
Well ready your bowels for evacuation, because here comes a real chocker: The private sector? yeah, it too needs checks and balances, and for exactly the same reasons, if you want a free market, you don't ask the very people who has the least reason to protect it to be it's guardians, that's like asking a rabid Jackal to babysit your child.