I think you're overlooking the fact that unionisation makes little difference, when there's a large number of workers chasing a limited amount of work.
If there's not enough work to go round, then some people will always work for less rather than have no work at all.
You can tell them they shouldn't, but they might be inclined to reply, well it's do that, or my family'll be homeless, -- are you telling me I should make my family homeless?
Are you?
top posting and thank you for the lesson in basic trade unionism .. it is sorely needed around here
( p.s. NOT sarcastic!)