How is inflation is SA currently? Inflation tends to hypertrophyze unions, because there comes a need to a common agreement to adjust wages across the board to keep up with prices.
The problem really is that when you have 25% unemployment, where those 25% are almost all unskilled then you work to eat and not much more. You don't have much bargaining power there. So again, if you're unskilled, oversupplied and are replaceable by machines, you should be very careful about what sort of demands you throw around. I'm not sure if unions are really conscious of this fact or just trying to appease the workers demands.