Unions do all kinds of wonderful things.
They make it incredibly difficult to fire under performing workers, for example. That lazy guy who never finishes anything on time? Yeah, can't fire him. Can't even discipline him.
Unions take your dues - which will not be small - and will use them to prop up politicians. Politicians that you may not like.
Unions may raise your wages, sure, but that will also raise the cost of your company doing business. That means your company will need to charge more, meaning more work for the non-union shops because they're less expensive.
Unions will make sure that you are promoted based on years of experience, not skill or knowledge. So that moron who doesn't know the difference between an integer and a float, but has been here 20 years? He's getting paid more than you and always will.
Speaking of, are you particularly valuable as an employee? That's nice. You may be super smart, very talented, incredibly fast at what you do, but too bad. You're getting union scale pay.
No, we don't need unions. Is your company crappy? Leave. Find a job somewhere else. That company will have to learn to treat their workers better or they'll be stuck with a perpetual revolving door, with no work getting done.
It worked at my company. We weren't being treated well. A ton of people quit. Company wised up, started treated existing employees better, increased pay and benefits. No union needed - just a free market.