Answer:
They're afraid that they might get fired if they decided to make a negative publicity toward the company.
Explanation:
Throughout the history, Employers have tendency to minimize the cost of running a business. Often times, this come a the expense of reducing the amount of money used to create safety measurements in workplace.
Currently, worker's right to report unsafe factory conditions are protected by the Occupational Safety and Health Administration. Workers in the past did not have such protection. Company could simply fire them and put them in a black list (this list will be shared to other companies so the workers can't find jobs anymore). So, a lot of them kept their mouth shut even if they knew they're risking their life in the factories.
