In my own words: A labour union is a group of workers who have banded together for better wages, benefits, and conditions at their workplace.
If you like those things, you should organize a union with your coworkers. If you want something beyond those things, form a union. If you already have those things, you should organize a union to make sure you keep them.
Of course, if only it was that easy to "just organize". Here's why I think it's hard to form a union:
Most people support unions. But some people, especially younger workers, don't even know what unions are. (I was born in the 90s and didn't know what unions really were until my mid-20s.) If there are less people in unions, then less people know someone in a union, let alone what unions actually do for workers.
Another issue is time and effort. Employers are good at squeezing hours and energy out of workers, almost always more than necessary. To maximize their profits, they minimize employee wages. They also minimize downtime: breaks, rest, even entire meals. Employers hate unions because it means they would have less control over these things. In turn, that means less control over how much they make off of the work their workers produce: the work you do.
Employers usually earn a lot more than their workers because that's how they, and people like them, designed the system. They use their excessive wealth, time, and control to prevent unions from forming. This is called union busting. Examples of union busting might include intimidation, creating divisions between you and your coworkers, and even stalling a first contract after you've won a union vote.
A coworker might mysteriously get a raise or benefits, while others get nothing. An entire staff might get punished for something one worker did. A coworker is reprimanded for speaking another language during their break. The list goes on.
All of this makes it really damn hard to organize a union. Many workers have low wages and low job security. It just so happens that these are the workers who need a union the most. Not all workers can afford that fight, because the system was rigged against us to begin with.
But no matter how much money employers spend trying to sabotage union efforts, workers still win. Workers still unionize. Workers were even poorer in the past, and they managed to win against their employers. The workplace is always where organizing begins. Talk to your coworkers. Share your grievances with each other. Think about what you'd like improved at work. There are never promises with union organizing, but you can win whatever you fight for, as long as you fight. The 8-hour workday was once 10, and even longer before that. It took time and effort from workers to fight for that, and win it, against employers and the elite. Things can change, and they should.
The workplace is where most of us are. Us being people who have to work for a living. We give the best hours, of the best days, of the best years of our lives to employers, as economist Richard Wolff once said. It's worth improving your workplace, for yourself and your coworkers.