Unions can vary considerably, and depend strongly on local culture. I'm fairly familiar with the UK, but unions here famously had a very antagonistic relationship with the business, in contrast to unions in, say, Germany.

There was a famous case, where Toyota (or some company like that) set up two identical car factories, one in Northern England and one in Germany. The one in Germany had vastly higher output per worker than the one in England, and a lot of the reason was down to the wildly different attitudes of the workers and the union - the one in England tended to put "tools down" for all kinds of silly bureaucratic reasons.

And certainly in other parts of the country and other industries - Clydeside ship building, say - unions were not blameless in helping along their decline - although the incompetence of management and the business helped there as well.