What exactly does it give the workers, better ways of dealing with management?
Without a union, you can ask management for stuff, but they can just say no. Your only recourse then is to quit, which wouldn't change anything when it's just one person.
With a union, a work stoppage is a possibility. Suddenly management have a reason to come to the negotiation table and make concessions.
A union can be just as exploitative as a company can. It's not all sunshine and rainbows.
The software industry has been regulated by demand over the last few decades. Demand is still extremely high for software devs. Managers know that employees can make moves because unemployment in our sector is something like 2%. I've worked in many industries in my life and I've never been chased down or marketed to move jobs as much as I have in software development.
A corporation is not entitled to anyone's labor.
If the union benefited from your LABOR then there would be no incentive for unions to strike.
Of course there are negotiations involved. Having workers be organized provides a better ability to ask for (and negotiate) things by banding together. As well as protections. Without, sticking your neck out—alone or in a small non-unionized group—can be a major risk.
High demand does not mean workers are not exploited (hi amazon), and employees organizing can provide protections and benefits for all staff, some of which may not be in the same “high demand” group.
For 99% of employees out their quitting isn't the threat you make it seem to be. As easy you make it sound to get a new job, its that easy for them to replace you. Then that new employee gets to deal with the same shit you left over. It never gets fixed.
Leaving and going somewhere new doesn't solve anything. for most people job hunting is just looking at piles of shit and finding which one stinks less.
Insurance at my current job is not great. I can't go to my boss and say I want better health insurance he would laugh me out of his office, but even if he could, why would he not just give me the better insurance from the start? If a Union went to management and said we demand better health care that carries weight. That would get something done.
It's not easy to replace tech employees at all. Even if there was an abundant supply of expert software engineers (there's not), it takes many months to ramp up on a new code base to optimal productivity and to learn the organization and domain requirements of a software product. That will never change.
An average tech company will spend tens of thousands of dollars to fill a position, not even counting initial salary and bonuses.
Leaving for somewhere better often does solve quite a bit. On my last job move my pay increased by 50%. If I had stayed at my previous company I'd be skating by with 4% raises.
On the whole the aggregate effect of employees moving around in a dynamic market creates the cush benefits and pay we see in this industry.
The reason they wouldn't give you specifically better insurance is because they have to negotiate a plan for everyone in the company. What is that costing them on paper? I don't know how many employees your company has or what their margins are or any details really, but it can be as much as $700-$1000 a month per employee for health insurance. If you've got 100 employees that's $100K a year.
No boss should "laugh you out of the office" for requesting that. But really, its an HR and Corporate leadership issue so you should take your grievances to those with the power to make the change and not your boss (unless you work directly for the CEO).