The story deals directly with the issues of worker rights, especially as they concern the right of workers to strike for better conditions. During the 1900s when the play was written, worker rights were still an unresolved issue, with unions starting to exert their influence over companies and boards, while the workers simply wanted to be treated and paid better. In the play, the exchanges between the board and the union representative are important in establishing the social themes; neither side is "right" or "wrong," but instead want the best outcome for their own people, regardless of the process.
HARNESS. I'm quite frank with you. We were forced to withhold our support from your men because some of their demands are in excess of current rates. I expect to make them withdraw those demands to-day: if they do, take it straight from me, gentlemen, we shall back them again at once. Now, I want to see something fixed upon before I go back to-night. Can't we have done with this old-fashioned tug-of-war business? What good's it doing you? Why don't you recognise once for all that these people are men like yourselves, and want what's good for them just as you want what's good for you [Bitterly.] Your motor-cars, and champagne, and eight-course dinners.
(Galsworthy, Strife, gutenberg.org)
This statement from the union rep shows how his union is not unconditionally behind the workers; when the workers are in line with union policy -- in this case, pay rates -- the union backs them, but when the workers exceed that limit the union disavows their cause as unreasonable. How is this appropriate? Because the union knows that if the workers are given high pay rates, the companies will eventually be forced to close because they cannot afford the labor. In similar ways, each side is shown from multiple perspectives, allowing the viewer a complex view of the issues. Additionally, the play's deep understanding of the issues themselves comes across in the dialogue, with various ideas and concepts presented in simple ways; this allows the viewer to be better informed about the social issues of the time while still enjoying the play as drama.