The purpose of government agencies like the Pure Food and Drug Administration and the Securities and Exchange commission is to protect American citizens.
For example, the Pure Food and Drug Administration works to ensure that companies do not produce foods that could be harmful to American citizens. Without this regulation, companies could essentially sell any food/product they want.
The Securities and Exchange Commission helps to ensure that American citizens are not being taken advantage of in the stock market. This agency helps to stop insider trading and aims to create an equal economic opportunity for all citizens.