My parents were union members at their cotton mill. Through the years the union got them things such as, vacation (mill shut down twice a year for 1-2 weeks and they drew unemployment for it), overtime (the legally required overtime pay), paid sick leave (really more you found someone who would trade days with you or you didn't get paid), and workers comp (the legally required amount). When the mill shut down to move to Mexico they made a big to do about how they had negotiated great benefits for those being laid off. In reality everything my parents got was state stuff given to all unemployed people anyway. The union did help them by giving them all the paperwork they needed to fill out though. After all the years of paying dues they pretty much got exactly what they could have gotten anyway.
This type of experience with unions is not uncommon in the South. And folks wonder why we don't like unions usually.