Unrestrained capitalism leads to slavery (J. Pournelle). So we have to regulate it so that it doesn't get to that state. Capitalism is built around exploitation; either workers, physical resources, or knowledge. This has the benefit of increasing prosperity over time, though at a cost. As unfortunate as these costs are, Capitalism is the worst economic system, except for all those other forms that have been tried from time to time.

(Apologies to Sir Winston Churchill)