> All you have is your ability to stop working. Which, indeed, can exert power –– But if you are poor how long can you really go without work before you starve to death?

When union workers strike, they do so collectively, which means that the bargaining power is not that of a single individual but that of the collective workforce. Employers often can’t just wait out a strike because they lose tons of money when all its employees aren’t working. The union’s strength lies precisely in this collective bargaining power.

Also, unions raise money to support striking workers and unions emerged initially in the jobs where workers were paid the least and exploited the most (see early 19th century textile workers in the U.S., for example). The decline of unions since then is a more complicated history but the reality is that unions most benefit the most exploited workers who would otherwise have no recourse as individuals. Collective support helps maintain workers throughout a strike.