Easier for the companies maybe but not the employees. Companies are almost always in a better position relative to employees when it comes to negotiation: they have more information, deeper pockets, and on an individual negotiation level have little need for a specific employee (especially in manufacturing jobs where the skill level is low). The employee on the other hand often has few options and if they do push for better wages can just be canned losing their healthcare and possibly pension (in the few places those still exist) because in manufacturing (and to be honest many other jobs) individuals are by design replaceable and largely interchangeable. In some areas there's only 1 or 2 employers for that type of job and moving for a better opportunity requires uprooting the lives of the rest of the family (children go to new schools and spouses have to find new jobs as well) with a lot of uncertainty about the new job.

To counteract this and get the employees a fairer share of the value they add to a company unions exist so that the power imbalance gets evened out between workers and management.