This is a good question. There are many reasons why consumer protection is important. Let me name a few of the reasons state and Federal government has provided protective laws and agencies.
First, when customers buy a product, they need to be protected for the simple reason that they can get hurt from hazardous products or materials. For example, if a vendor sells a car that does not work well, then someone can die. Or if a company sells a product for children, and the product does not work well, many children can get hurt. Something simple as using lead paint can hurt children.
Second, since corporations are powerful, there needs to be other protective measure to ensure that customers are looked after. It cannot only be about the bottom line of profits. For example, warranty standards, guaranteed by the Magnuson-Moss Act (1973), are important to ensure that the customer is buying a product or service that works.
All of these things give consumers protection for their expectation that companies deliver products and services that are of a legal quality.