The question I have is if wild foods are contaminated, why wouldn't cultivated foods, which exist in the same environment, not suffer the same way?

Fish is a great example. Here in PA we have many warnings NOT to eat too much (more than a serving a month) of any fish caught in any body of water. So Trout, which is farm raised and released into the wild, isn't a meal choice for regular eating. Wild Greens? Too toxic (they say) but why is this the case when the farm next to the place where I pick wild greens sells their food as "safe" .