It makes sense in the context of the history of unions and legislation regarding them in the US. The overall idea is that both employers and unions are limite

It makes sense in the context of the history of unions and legislation regarding them in the US. The overall idea is that both employers and unions are limited in what they can do to each other, and in exchange we have less violence of the sort that happened when companies broke strikes with hired guns like the Pinkertons. Like with many regulations, both sides think they are getting screwed more than the other side.