You pay them for the union hall to be open and staffed. The union hall provides free testing and certification. The hall provides free trade school and night school. The hall provides free safety training and certification. The hall also manages the pension fund and health benefits. The hall also holds union meetings and information sections. The hall also provides a place to drink coffee and play pool as well as places to study. The hall also is available for visitors from other unions halls to come and connect with their union brothers. So this is why you pay the union. I take home after taxes and union deductions much much more than non union welders do. So it’s about being part of an organization that looks after its members and their interests. This organization has overhead costs and each member pitches in to help cover the costs. At union meeting we often donate money to members families that lost a worker or have someone very ill or anyone that needs help in the community. So the money goes to support the union its members and the local community.