Once unions lost their legal ability to strike, once legislation that gave them little hope of collective bargaining was enacted (thank you, Mr. Reagan and almost everybody since), they lost the ability to work FOR you, and rapidly became a minor (or major, depending on the venue!) pain in the rear that couldn't really help you.

But yes, once upon a time, they did a lot of good.

Your rule, re-written to reflect today's reality is, 'Work hard, get paid ONLY what they are willing to give you'. And they keep the lion's share for themselves.