Pure capitalism favors the wealthy and the unscrupulous. That is if there are no laws in place protecting peoples rights then the business owners have little incentive to treat there employees well (they will trade short term profits over long term stability.

On the flip side a pure communist system favors the lazy since there is little to no reward for doing more than the minimum. That is to say the status quo is unchanging.

This is why we have government, to correct the selfish nature of capitalism, while hopefully still retaining the innovation and drive that it produces (winner take all is a strong motivator).

This only works in the long term if government is fair and balanced, looking out both for the interests of business and society (the poor, the environment, the common spaces, etc). And where an idea like socialism actually strikes a good balance between both extremes.

The idea that the markets will sort themselves out is a fever dream thought up by the right. The markets will quickly consolidate into monopolies and then exploit there power. It is only fair competition that produces benefits. And that is an unstable balance that must be carefully maintained by outside forces (government).