I wonder if it might be a bit of a challenge for unions to adapt. In order to adapt, generally people need to be able to not necessarily give up things but they have to step outside of the established norms at the very least. So there's a certain degree of instability or volatility associated with adapting.
It seems to me that businesses usually don't have too much of a problem with adapting. That's a gross generalization but I think it's accurate to say that businesses or business minded people are always looking for an edge and thus already have that mindset to adapt. I'm not sure if some of the unions here in the US have that mindset. I mean part of joining a union is seeking out the better wages, benefits, fairness, etc and the stability associated with those things. When we're forced to adapt to things, stability kind of goes out the window although not necessarily permanently.
"Don't confuse facts with reality."
-Robert D. Ballard