Some of the most important things unions negotiate for aren't about pay and benefits. They negotiate things like working conditions, handle disputes, and the like.

Those things are usually much more important than pay and benefits, and when union negotiations stall, it's more usually about that sort of thing than about money.

I hate to bring up the old example, but it's used because it nicely illustrates the value of unions for everybody -- not just the union members. Things like having a 40 hour workweek and weekends only happened because of unions.