Right, but ultimately a union is still a democracy, and the bureaucracy has to stay in power. That seems a lot harder to do if you don't actually have your constituents interests at hand. I will grant that in a large enough union I could see bureaucracy being a problem, like that. But also the fact that unions have been gutted for power (in the US) means that union officials aren't nearly as bad as the equivalent groups in a more powerful institution. Also it means that they're still in the stage where most unions could stay vigilant to avoid it.