The "competitiveness of a company on the global market" isn't the be-all, end-all. The phrase itself belies your point: if we as a society wanted to, we could place tariffs equivalent to the cost of providing a humane workplace for packaging workers, while also requiring our own companies to do so. This would eliminate the competitive edge issue, while also allowing other countries to engage in free trade with us if they pass laws protecting their own laborers from workspace exploitation.

We simply choose not to, for certain values of we (read: members of the finance capital rentier class that dominates American political discourse).