In my country, the opposite is the case.
There is one central body for Unions and their bosses have all been bought off and socdemised (the head of that body visited the socdem party and the conserf party, but refused to visit the radical left party).
They failed to stick up to their members, they got poorer, and now they can no longer afford Union membership.
Just like Socdems, the Unions perpetrated their own downfall.