It isn't up to Union leadership to decide if they want to accept the contract or not. They try to negotiate the best contract for the union membersand then can recommend what to do, but it is up to the union members themselves to decide by voting on the contract. "THE" union doesn't have a say just the members.
So basically people are paying union dues for someone to negotiate a contract with Disney that very likely will not change. And the reason they continue to do this is?:shrug:
I think the best way they could give themselves a raise is to dissolve the union and pocket the dues.