A "free market" approach would only work if everyone has enough money to be able to turn down offers that don't appeal to them. For companies that means not selling goods for less profit than they want (meaning it's very expensive). For employees that would mean not taking jobs that don't compensate them properly. For employers that means not hiring people that want more than they want to pay out.
Since in the real world all the money seems to start in the hands of the people doing the hiring, they get to dictate the terms of employment, and if prospective employees don't take what they're offered, they will soon be homeless and will starve.
People used to be able to farm for their own food and trade excess to make their living, so they didn't need to depend on others for employment. But that's not really possible today without the large amounts of money needed to start such an endeavor: the land, equipment, seeds and water for farming cost more money now than they ever have in history.
Without a government involved as a third party, people with excess money will always be able to dictate terms to those without, and can keep them in that state. This isn't necessarily out of any nefarious will on the parts of those with the money, though it frequently is. How else can we explain American companies (Hanes and Levis most prominently) fighting to keep Haiti from instituting a $.21/hour minimum wage? Less than $2.00 a day - this is far less than street buskers can make in any large American city. I've met some that make more than 50 times that from street performances.
The problem with government involvement is when those with money are allowed to influence the government with it - which is how Hanes and Levis were able to persuade the US State Dept. to pressure Haiti to not institute that minimum wage. Imbalances of money caused failures in government for both the US and Haiti to protect individuals.