Because regulations in America almost always favor big corporations and not consumers/independent businesses.

I've lived both in UK and US and the quality of food, medication, etc is night and day. You can compare the ingredients of big mac in US and UK and you'll see what I mean.

I actually recently watched a great show called "Dopesick" that tells the story of how American opioid crisis began. I think it does a great job explaining how stupid and ineffective FDA really is.