Musicians Union Necessary?

I'm just curious if anyone here is in the musicians union. If so, why?
I joined for about a month maybe 10 years ago and basically quit again straight away because I couldn't see the point in paying money when you get nothing in return. I've never needed a membership since then despite playing tons of bars and schools etc. so I guess I'm wondering what the purpose is of joining them.

If you get screwed they do your complaining for you.

some gigs, such as theater, casinos, and television, are unionized (is that a word?) so if you want to play them you have to be union.
The union is not responsible for getting you work, they only represent you if you get sheistered (making up my own vocab here)
The union also moderates the pay for the above mentioned venues.