It’s important to know that both the FDA and the USDA are in charge of inspecting food, and which food is covered by which agency can be complicated.

FSIS [under the USDA] conducts continuous daily inspections of foods in its domain, whereas FDA inspections have no regular schedule. The FDA is more likely to inspect only after a tip about a possible food safety violation, so random inspections can occur up to 10 years apart or, in rare cases, not at all.

“It’s not that they don’t want to inspect more, they just don’t have the funding,” Raymond says.

This inspection imbalance means that pepperoni pizza, because it contains meat, has ingredients that will be inspected three times before the product hits the grocery store freezer: at the slaughterhouse, the packing plant and the pizza factory. A vegetarian pizza produced at the same facility, however, will probably not undergo any inspection.

And in regard to the FDA being not allowed to regulate:

[The Dietary Supplement Health and Education Act of 1994] placed the burden of proof concerning dietary supplement safety on FDA, requiring the agency to show that a dietary supplement ingredient is adulterated rather than requiring the manufacturer to prove a supplement is safe prior to marketing. This is in contrast to new food additives, which require submission of safety information in a food additive petition prior to marketing, or drugs, which generally require submission of safety data as part of a new drug application prior to marketing.

At least with dietary supplements, they can’t make a new product guarantee it’s safe, the FDA needs to already know something is dangerous before it can force a recall.

If you’d prefer to learn more through a comedian, John Oliver covered this topic a while back https://youtu.be/Za45bT41sXg