Customers can and do independently test their products when they care, from the UL to review sites to kosher certification to gluten-free certification to animal welfare standards at grocery store deli counters. The free market is adequately capable of answering these questions.

When customers actually care enough to pass a law, they can. That's why certain practices are illegal. Other ones aren't because they don't want their taxes increased to fund investigations they don't care about. When the government starts enforcing protections for people's own good because they know better, you no longer have a free market.