Once again, negotiating industry wide wages for a category of worker is the only way to eliminate wages as a competitive factor in pricing and in profits. If everyone in the industry has to pay the same wages that eliminates the pressure for any one company to push wages down in their company to gain an advantage over other companies. They have to compete in other areas to earn business.
It also reduces friction between the management and the workers in a company if wages are negotiated industry wide.
It is not just wages, it is working conditions. Employers are reluctant to, for example, reduce the work week or to increase vacation time because of competitive pressures. If the changes are industry wide this problem is eliminated. Reducing the work week is an obvious solution for under employment and for the displacement from automation.