Unions mostly get talked about as a way of helping workers, but I think their ability to solve collective action problems and improve economic output when properly structured is vastly underrated
For example, in a fluid labor market there's a disincentive to train workers, because a company's investment in training may be poached by another firm. Unions can, in collaboration with employer groups, solve this problem by coordinating training
Sectoral bargaining can also address the prisoners dilemma of wage-price inflation. Under individual bargaining, every worker has incentive to maximize wage growth, even if this leaves everyone worse off due to resulting inflation peoplespolicyproject.org/2018/05/03/cou… 
This type of coordination can also help maintain international competitiveness. Under coordinated sectoral bargaining, wages in service industries (and other non-tradable sectors) are often pegged to tradable sectors so they can remain competitive
