system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Please explain the benefits and purpose of a union to me.

Dear Reddit,   I understand that this could be a volatile ELI5,  since unions and the NMB are kind of a polarizing topic.  
A little background about myself and the reason I am requesting this ELI5.  I am a current employee of one of the largest airlines in the world.   I have always been a pro-union guy and have enjoyed the security that having a union provided.   Not too long ago we merged with (were acquired by)  another airline and the union was voted out.   This was due in part because we,  the unionized workers of the acquired airlines,  were out numbered almost 2:1 by the non-unionized employees at the other airlines.   In the next couple of months we will be getting another vote to try and get a union back in,  and I really need a way to explain to people, in simple, 5 year old terms,  why this is good for them and their family,  and is much more valueable than the $55 a month union fee that they seemingly can't afford to give up. 

Thanks!
gpt
The primary benefit of a union is the collective bargaining aspect. If the entire workforce negotiates together you have far more leverage than you would negotiating one on one with HR, et al.

What you have to weigh now is the value of the 55/mo versus the issues that you want to negotiate. The best way to help illustrate this in a roughly ELI5 way is to help them see the value that 55/mo brings.

Would you pay 55/mo for an extra week of vacation?

Would you pay 55/mo for a guaranteed limit on hours worked per week?

Would you pay 55/mo for a guaranteed minimum on hours worked per week?

Would you pay 55/mo to ensure adequate safety/precautions etc?

And you go on and on, the main counter argument you have to overpower is whether or not the abuses (actual or merely perceived) warrant coming together and funding the union. If your employer generally treats you well, why would you unionize? The other counter issue you need to consider is mobility. If workers can't move around or replace the job, then they are less powerful and need bargaining assistance, if it's easy to move from job to job then the need to make THIS job better is reduced.

I know this is not quite ELI5, but that's the argument you would have to make.