Money is probably the least important thing in a union contract. It's always about rights.
Unionizing is the only way to escape the prostitution-like relationship of paid work.
Accepting to being paid more is just accepting being a more expensive prostitute.
"Here's $100, now you do what the man says... Ok .. $200?"
No, it's never okay. No amount of money can ever make it okay. You should have the rights to choose how and when you do the thing that you're offering as a paid service. That's why you need a clear contract that outlines all of your rights.
In this case it's about termination without cause.
As an employee, you'll want a binding contract, so you can plan ahead. Termination without cause is the employers trick to keep you on a one sided contract in which you'll have to dance like a bear in a Russian circus, while the employer has no obligation to keep you fed once the show is over.
The reason they strike is that the employer has already abused this power.